I. Introduction
On 21 August 2015, British Prime Minister David Cameron authorised the killing with military force of a British national, twenty-one-year-old Reyaad Khan. Khan and two other men riding in a vehicle with him were blown to shreds by Hellfire missiles launched from a remotely piloted drone. The attack occurred in Syria, despite the fact that the United Kingdom Parliament had voted to restrict UK involvement in the Syrian Civil War. The Prime Minister declared the killings a lawful exercise of Britain’s ‘inherent right to self-defence’Footnote 1 against a ‘very real threat’.Footnote 2 The British suspected Khan of recruiting individuals to ISISFootnote 3 and of plotting terrorist attacks to be carried out in the UK.Footnote 4 A few days later, the United States also conducted a drone attack in Syria and announced with a ‘high level of confidence’ that it had succeeded in killing another twenty-one-year-old British national, Junaid Hussain.Footnote 5 Hussain was also a member of ISIS, as well as a convicted computer hacker and suspected plotter.Footnote 6
ISIS, the group to which Khan and Hussain belonged, is part of a long line of non-State organisations that have used terrorist tactics and armed force to achieve political ends. ISIS emerged after a break with another such group, Al-Qaeda,Footnote 7 and bears comparison with earlier Middle East groups such as the Palestine Liberation Organization (PLO). The PLO formed to oppose the establishment of Israel in the former British Mandate of Palestine. Israel itself came into being in part through the efforts of organisations such as the Irgun and the Stern Gang.Footnote 8 The African National Congress (ANC) formed in the 1950s to oppose white minority rule in South Africa. The ANC employed violence until its leader, Nelson Mandela, famously embraced non-violent resistance.Footnote 9 The list of examples could continue back to Antiquity.
Governments have responded to these groups in different ways. The United Kingdom and United States long took the position that lawful and effective counter-terrorism involves law enforcement measures, not military force. Their position began to shift as the Cold War ended and new weapons technology emerged. First the US and then the UK put forward new legal arguments aimed at justifying the use of military force.Footnote 10 The UK’s earlier commitment to law enforcement is seen in its response to the ‘Troubles’ in Northern Ireland. The UK tended to treat the Irish Republican Army (IRA) and its offshoots as criminal organisations, not as insurgencies. When the UK joined Additional Protocol I to the 1949 Geneva Conventions on the protection of victims in armed conflict, it appended this understanding:
[T]he term “armed conflict” of itself and in its context denotes a situation of a kind which is not constituted by the commission of ordinary crimes including acts of terrorism whether concerted or in isolation.Footnote 11
The United States took a similar position, refusing to join Additional Protocol I out of concern that the Protocol treats individuals using terrorist tactics in liberation struggles as combatants.
Like the UK, the United States policy applied national criminal law to terrorist suspects and organisations. President Ronald Reagan explained that terrorists have and should have the status of criminals, not combatants or irregular fighters in armed conflict.Footnote 12 He said that to ‘grant combatant status to irregular forces even if they do not satisfy the traditional requirements … would endanger civilians among whom terrorists and other irregulars attempt to conceal themselves’.Footnote 13 Reagan took the first significant step away from this policy in 1986, however, when he ordered an air attack on Libyan military sites following violent incidents linked to the Libyan government under Muammar Gaddafi. In 1998, US President Bill Clinton extended Reagan’s tactic to non-State actors, bombing Sudan and Afghanistan where Al-Qaeda, known to lack State sponsorship, had camps.Footnote 14
In 2000, Clinton modified a presidential executive order banning assassination that had been in place since the 1970s. By doing so he removed a domestic legal obstacle to the CIA deploying the newly weaponised Predator drone to hunt for and assassinate Bin Laden.Footnote 15 The CIA failed in that attempt, and 9/11 followed. By 7 October 2001, the US and UK were at war in Afghanistan.Footnote 16 The US then began drone-launched missile attacks targeting individuals in Yemen, Pakistan, and Somalia.Footnote 17 In 2008, the CIA joined Israeli intelligence in using a car bomb to assassinate a member of Hezbollah in Damascus, Syria.Footnote 18 The United States has continued to expand the list of non-State actors, locations attacked, and weapons used in targeted killing operations.Footnote 19
In 2015, the United Kingdom also abandoned its approach of treating terrorism as a law enforcement matter with its drone attack in Syria. Cameron’s invocation of Article 51 in his justification fits a scholarly trend which began in the 1950s, arguing the Charter should be interpreted to allow States to use armed force in more situations than its terms allow.Footnote 20 The first proposals for such ‘flexible’ interpretation relied on policy arguments.Footnote 21 Over time the proposals evolved to incorporate examples of State practice, asserting that practice subsequent to the Charter’s adoption is capable of altering the meaning of its terms.Footnote 22 The underlying assumption appears to be that desiderata such as security from terrorism or the advancement of democracy have a higher moral status than the prohibition on force and that the violation of an inferior principle in the pursuit of a superior one should be permitted or excused.Footnote 23
This chapter examines these lines of argument. It finds each inadequate to justify a State’s use of military force against non-State actors on the territory of another State, when the force is used without the territorial State’s express consent. The situations under consideration are comparable to the UK and US attacks in Syria targeting ISIS members in August 2015. Section II presents a solidly evidence-based understanding of the law on the use of force against non-State actors. This reading of the law relies on UN Charter provisions and related general principles of international law. It also includes the negotiating history of the Charter, as well as resolutions and decisions of UN organs since 1945. The law prohibiting the use of force is shown to be ius cogens, from which no derogation is permitted. Ius cogens and the general principles relevant to the use of force do not emerge from the positive law sources of international law – treaty and custom – but are rather discerned, as will be discussed briefly in this section and in greater detail in section IV.
Before reaching that discussion, section III presents three prominent scholarly challenges to the understanding of the law set out in section II. These ‘pernicious doctrines’ rely on policy, State practice and a reassessment of international law’s normative hierarchy to claim a far broader and more flexible right of States to resort to armed force against non-State actors than the analysis in section II reveals the law permits.
Section IV responds to these challenges to the law on various grounds, including, most significantly, by explaining how the methodology used by advocates of flexibility is inappropriate for analysing peremptory norms and the general principles that govern the use of force. The section will emphasize that peremptory norms are non-derogable. They are derived from ancient and universal moral principles. They are superior to contrary policies and principles of a lesser status. Each peremptory norm is equal to the other peremptory norms. They are not subject to change through the operation of standard treaty and customary international law processes for creation and modification, nor may derogation occur through reinterpretation. Peremptory norms reflect the international community’s highest ethical values, expressed as legal principles. No superior laws exist to excuse or justify the breach of a peremptory norm.
Arguments to expand the right to resort to force not only conflict with the peremptory prohibition on the use of force, they also conflict with the human right to life. The International Covenant on Civil and Political Rights affirms:
Every human being has the inherent right to life. This right shall be protected by law. No one shall be arbitrarily deprived of his right to life.Footnote 24
Any killing that does not conform to the law governing resort to force, the law governing the conduct of armed conflict, or peacetime criminal law, violates the right to life. It is a right so fundamental to all of law that some scholars have discerned that it, too, is ius cogens.Footnote 25
The analysis in section IV also shows that even ignoring the special status of ius cogens and general principles, expansionist challenges to the prohibition on the use of force are unpersuasive. Under standard principles of treaty interpretation, the case for broader, more flexible rights to use force is weak at best. This should come as no disappointment, however, given the data showing that military force is a poor means of ending non-State actor violence. The confidence in military solutions reflected in the expansionist approach is misguided. The far better approach lies in promoting political engagement and respect for the rule of law.
II. Evidence of the Durable Meaning of Self-Defence
In 1945, the United Nations was founded for the express purpose of preventing war. The UN Charter preamble begins by affirming that the peoples of the United Nations desire to save ‘succeeding generations from the scourge of war.’ In Article 2(4) of the Charter, member States promise to ‘refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the Purposes of the United Nations’. Chapter VII sets out the only two exceptions to the Article 2(4) prohibition. States may use force in self-defence under the restrictive terms of Article 51 or when they have UN Security Council authorisation, per Articles 39, 41 and 42.Footnote 26 Much of the rest of the Charter addresses the underlying causes of armed conflict by promoting respect for human rights, the peaceful resolution of disputes, and economic development. Beyond the Charter, principles of State responsibility as well as the general principles of necessity and proportionality constitute main aspects of the ius ad bellum. The meaning of relevant Charter terms and related principles are found by analysing the text of the Charter, the drafting history of the Charter, and decisions of the UN General Assembly, International Court of Justice (ICJ) and Security Council. The approach is different from that of Christian Tams who relies on these sources but also believes State practice can modify the meaning of the Charter’s terms to permit more force.Footnote 27 Yet, permitting more force conflicts with the ius cogens status of the prohibition. Ius cogens and general principles are not modifiable through the impact of State practice. The law of self-defence may change over time but only in the direction of greater restrictions on the right to resort to force.Footnote 28
A. The Terms of the Charter
1. The Prohibition in Article 2(4)
Article 2(4) forms the primary international legal rule with respect to the use of force. Any lawful resort to force is an exception to the Article 2(4) prohibition. The accurate approach to arguing whether a use of force is lawful begins with Article 2(4), then identifies the exception to it that makes the use justified.Footnote 29 This structural aspect of international law on the use of force is significant for several reasons. Exceptions to a general rule tend to be narrow.Footnote 30 In case of doubt as to whether an exception applies, standard legal interpretation supports the primary rule in distinction to the exception. Also, exceptions are interpreted in light of the object and purpose of the primary rule.
Despite this understanding of Article 2(4), within a few years of 1945, several international law scholars began offering arguments aimed at limiting Article 2(4)’s scope. Perhaps the best-known early scholar advocating a broader right to resort to force was the University of Sydney’s Julius Stone. He was a harsh critic of the UN, writing an opinion piece in 1950 about the new organisation titled, ‘A Mad Hatter’s World Tea Party’.Footnote 31 Soon after the op-ed, he put forward an interpretation of Article 2(4) that functionally eliminated its restrictions on a State’s right to use force.Footnote 32 In 1958, Stone published a book defending Israel’s attack on Egypt during the Suez Crisis, asserting that Article 2(4) only restricted a State’s use of force aimed at interfering with the territorial integrity or political independence of the State being attacked.Footnote 33 Stone did not take Article 2(4) as his starting place, but Article 51, casting it as a permissive right, a tool to seek justice, rather than as an exception to a general prohibition.Footnote 34
Stone plainly wanted to expand the right for some States to use more military force irrespective of the Charter’s terms. He took no account of the objects and purposes of the Charter, of the negotiating history,Footnote 35 or of the status of Article 2(4) as ius cogens. He attempted to undermine the legitimacy of the Charter restrictions on the use of force by tainting them as mere concessions to great power demands.Footnote 36 As will be discussed next, Article 51 was a concession, but to Latin American States, not to Stone’s great powers.
2. The Exception in Article 51
Article 51 was a late addition to the Charter and was drafted not just as an exception to Article 2(4), but in deference to the Security Council’s power to authorise the use of force. States may use force in individual or collective self-defence if an armed attack occurs until the Security Council acts. It is worth setting out the entirety of Article 51 to underscore the restricted and contingent nature of the exception for self-defence:
Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.
‘Self-defence’ is a term of art in international law and a term that was well known to the drafters of Article 51. In an exercise of lawful self-defence, a State that is a victim of an armed attack may counter-attack using significant offensive military force on the territory of the State legally responsible for the initial, triggering attack.Footnote 37
Article 51 is understandably restrictive in light of Article 2(4) and the role created for the Security Council. Article 51 qualifies self-defence as an ‘inherent right’, or ‘droit naturel’ in the French version of the Charter, but one that is severely limited. In the same sentence in which self-defence is referred to as an ‘inherent right’, Article 51 restricts the exercise of that inherent right to cases where an ‘armed attack occurs’. The armed attack requirement is an objective and restrictive condition on the use of force. It is a critical feature of the practical design of the Charter. The French version of Article 51 indicates an even higher threshold. Force may be used in self-defence not just upon an armed attack but after ‘agression armée’ (armed aggression – more than a single attack). Article 51 provides further restrictions by requiring States to immediately report their actions to the Security Council. The use of force in self-defence is envisaged as a short-term emergency measure until the Security Council can act.
B. The Drafting History of the Charter
Given the early arguments by Stone in favour of interpreting the Charter so as to expand the right to use force, it is helpful to return briefly to the drafting history to indicate the intentions behind the words actually chosen. In 1938, United States President Franklin Roosevelt assigned a US State Department official the job of drafting a new treaty for a new world organisation to replace the League of Nations, which had failed to prevent the Second World War.Footnote 38 Article 51 was added in 1945 during the final negotiating session in San Francisco.Footnote 39 The drafters did not intend to provide a permissive basis for resorting to force as Stone and others have contended. The purpose was to allow the creation of an organisation prepared to act in collective self-defence should the need arise.
Article 51 was a late addition, not part of the plans for the Charter from the outset, in contrast to Article 2(4). The new organisation charter was to have a more straightforward and direct prohibition on the use of force than the Covenant of the League of Nations.Footnote 40 The new prohibition was inspired by a renewed global commitment to ending war, as well as the major US diplomatic initiative in the inter-war period, the Kellogg–Briand Pact. The Kellogg–Briand Pact or Pact of Paris was concluded and came into force in 1928 with just two substantive paragraphs:
Article I. The High Contracting Parties solemnly declare in the names of their respective peoples that they condemn recourse to war for the solution of international controversies, and renounce it, as an instrument of national policy in their relations with one another.
Article II. The High Contracting Parties agree that the settlement or solution of all disputes or conflicts of whatever nature or of whatever origin they may be, which may arise among them, shall never be sought except by pacific means.Footnote 41
The Kellogg–Briand Pact says nothing about self-defence, but scholars have commented they assumed the Pact did not interfere with the customary international law right of self-defence.Footnote 42 Like the Pact, the early drafts of the Charter had no reference to self-defence, which is why the Latin American States requested that it be added. The main Charter innovation over the League was the introduction of a powerful Security Council authorised to take measures to respond to breaches of international peace and security.Footnote 43 It would be the new council’s job to respond to any violations of Article 2(4).
The US not only drafted the Charter, it organised and led the negotiating conference in 1945 at San Francisco to reach agreement on the final version. The records from San Francisco clearly indicate the understanding that Article 2(4) was intended to cover the use of armed force in distinction to more general forceful or coercive measures not involving the use of force, such as economic sanctions or minimal uses of force involved in law enforcement.Footnote 44 The States involved expressed their interest in banning the first use of military force beyond any de minimis use.Footnote 45 The United States had carefully chosen the terms of Article 2(4). The references to ‘territorial integrity’, ‘political independence’ and, especially, ‘in any other manner inconsistent with the Purposes of the United Nations’ were meant to generate a broad prohibition. A member of the US delegation, in responding to a question by the Brazilian delegation on Article 2(4)’s scope, said that ‘the authors of the original text intended an absolute all-inclusive prohibition; the phrase “or in any other manner” was designed to insure that there should be no loopholes.’Footnote 46
When the Latin American States arrived in San Francisco, they were in the midst of organising a new collective security system for the Americas. They became concerned during the conference that the terms of Article 2(4) would restrict the right of a State to come to the assistance of a State attacked in violation of the new prohibition. They then requested an additional provision making it clear that members of the Rio Treaty Organization would be permitted to treat an attack on one of them as an attack on all.Footnote 47 Article 2(4) could be construed as requiring a State to get Security Council authorisation prior to assisting another State fighting in self-defence. Thus, for the purposes of allowing the Rio collective self-defence arrangement to proceed upon an armed attack, Article 51 was added to the Charter permitting assistance pending Security Council action.Footnote 48
The US delegation provided the draft of Article 51, placing it in Chapter VII of the Charter, which otherwise sets out the Security Council’s power to respond to breaches of international peace. The formulation has been criticised as clumsy,Footnote 49 but it accomplished three objectives: it preserved the far-reaching general prohibition on the use of force in Article 2(4) by limiting the right to a response to an armed attack; it clarified the right of other States to join in collective self-defence, and it maintained the Security Council’s supremacy in all matters related to the use of force.
The US delegation discussed the possibility of allowing resort to self-defence in anticipation of an armed attack. This, however, was rejected. One member of the delegation, Senator Harold Stassen, explained: ‘We did not want exercised the right of self-defence before an armed attack.’Footnote 50 Indeed, only a narrow right of self-defence would be consistent with other provisions of the Charter. In addition to the general prohibition on force in Article 2(4), the provisions of Chapters VII and VIII giving the Security Council principal authority over peace and security made sense only in the case of a narrow exception for the use of force by States acting independently of the Security Council. The terms of Article 51 reflect the Security Council’s central role, as does Chapter VIII’s Article 53 requiring prior Security Council authorisation for all uses of force by an organisation other than one responding in collective self-defence as provided for in Article 51.Footnote 51
The UN Charter’s drafters were well aware of the justification Axis States had used for violating the League Covenant and Kellogg–Briand Pact during World War II. They used arguments developed by their lawyers based on self-defence. The German Reich strived for ‘Lebensraum’ in order to ensure – so they claimed – survival.Footnote 52 Germany invaded Norway and the Low Countries citing a right of self-defence to pre-empt any future attacks by those States.Footnote 53 Imperial Japan made similar arguments for its territorial aggression in Asia aimed at securing vital natural resources, especially oil.Footnote 54 The new United Nations would permit unilateral self-defence only in cases where objective evidence of an emergency existed for the entire world to see, namely an armed attack. Other, less tangible or immediate threats required the collective scrutiny of the Security Council before the use of force would be permitted. The collective deliberation of the Council replaced the unilateral judgment of the potential victim.
C. The Understanding in UN Organs
Three UN organs have regularly taken up consideration of the Charter principles on the use of force. Their deliberations, resolutions, and decisions are the most relevant sources for understanding the terms of the Charter on self-defence against non-State actors. Various efforts of the Secretary-General have been relevant and will be mentioned as well. Again, the discussion below seeks to show how these important bodies have understood the Charter, not how their activities purport to modify it.
1. The General Assembly
In 1970, on the twenty-fifth anniversary of the adoption of the UN Charter, the General Assembly adopted its Declaration on the Principles of International Law Concerning Friendly Relations and Cooperation Among States in Accordance with the Charter of the United Nations.Footnote 55 The first three principles in the Declaration relate to the use of force and generally follow the basic understanding outlined above. These include:
(a) The principle that States shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the purposes of the United Nations,
(b) The principle that States shall settle their international disputes by peaceful means in such a manner that international peace and security and justice are not endangered,
(c) The duty not to intervene in matters within the domestic jurisdiction of any State, in accordance with the Charter.Footnote 56
The elaboration of Principle (a) in the Declaration includes the statement:
Nothing in the foregoing paragraphs shall be construed as enlarging or diminishing in any way the scope of the provisions of the Charter concerning cases in which the use of force is lawful.Footnote 57
Principle (b)’s further elaboration emphasises that
armed intervention and all other forms of interference or attempted threats against the personality of the State or against its political, economic and cultural elements, are in violation of international law.Footnote 58
The comment to Principle (c) includes the duty on all States ‘to refrain from organizing, instigating, assisting or participating in acts of civil strife or terrorist acts in another State’.Footnote 59 At the end, the Declaration reaffirms that States have a duty to fulfil their Charter obligations in good faith together with their general obligations under international law.
While the Declaration generally supports the Charter as adopted, it also affirms the right of self-determination in a way some scholars see as supporting a right to intervene on behalf of non-State actors fighting for regime change or secession. If the analysis of the prohibition offered here is accurate, if such intervention involves military force it violates Article 2(4). As will be discussed in the final section of the chapter, section V, support for self-determination should not involve military force.
Four years later, the General Assembly adopted the Definition of Aggression. In the preamble to the Definition, the General Assembly expressed the view that ‘aggression is the most serious and dangerous form of the illegal use of force.’Footnote 60 During the preparatory discussions of the Definition, delegates recalled that the Nuremberg Tribunal referred to aggression as the ‘supreme international crime’.Footnote 61 The Versailles Treaty of 1919 had provided for a special tribunal to try the German Kaiser for ‘a supreme offense against international morality and the sanctity of treaties’ in waging the First World War.Footnote 62 These references to ‘supreme’ and ‘international morality’ reflect an understanding by member States of the peremptory character of the prohibition on force.
In defining this most dangerous form of illegal force, the General Assembly incorporated two approaches. It provided both a general purpose description in Article 1 as well as an illustrative set of examples in Article 3. The Article 1 description is based on Article 2(4). It describes aggression as ‘the use of armed force by a State against the sovereignty, territorial integrity, or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations … ’. Article 2 then provides that any first use of force in violation of the UN Charter is prima facie evidence of an act of aggression. The acts listed in Article 3 ‘are not exhaustive and the Security Council may determine that other acts constitute aggression under the provisions of the Charter’. Thus, the General Assembly foresaw the expansion of the list in the future. There is no hint of the possibility of moving in the other direction.
Acts constituting aggression trigger the right of self-defence when the act is on a significant scale, such as invasion of territory, bombardment of territory, blockade of ports, attack on air, sea or land forces, and the ‘sending … of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another State of such gravity as to amount to the acts listed above, or its substantial involvement therein’.Footnote 63 The last example is perhaps most relevant respecting non-State actors. The term ‘sending’ is critical. It refers to a sovereign State sending a group to fight, which implicates a sovereign State’s responsibility. The Definition does not support self-defence against a State bearing no legal responsibility for a non-State actor’s conduct. The Definition also introduces some conceptual and normative confusion. It uses language similar to the Declaration on Friendly Relations respecting assistance to non-State actors, confirming their right to ‘struggle’ and to ‘seek and receive support’.Footnote 64 To be consistent with the Charter, outside assistance to groups seeking to expel colonial or occupying powers would have to be non-military. The Definition of Aggression provides little solid evidence in support of arguments seeking to expand the right to use force. It is another intentionally vague provision that can hardly alter a treaty term, even one open to change.Footnote 65
In 2003, following the invasion of Iraq by the United States, United Kingdom, Poland, and Australia, the then UN Secretary-General undertook a review of UN principles and institutional processes related to the use of force. The Secretary-General’s High Level Panel on United Nations Reform, reporting in December 2004,Footnote 66 and the Secretary-General’s own report of March 2005,Footnote 67 both discussed some of the expansionist proposals but reaffirmed that any lawful use of force outside the terms of Article 51 required Security Council authorisation. These restatements of the Charter were fully accepted at the 2005 United Nations World Summit:
78. We reiterate the importance of promoting and strengthening the multilateral process and of addressing international challenges and problems by strictly abiding by the Charter and the principles of international law, and further stress our commitment to multilateralism.
79. We reaffirm that the relevant provisions of the Charter are sufficient to address the full range of threats to international peace and security. We further reaffirm the authority of the Security Council to mandate coercive action to maintain and restore international peace and security. We stress the importance of acting in accordance with the purposes and principles of the Charter.Footnote 68
The only relaxation of the Charter’s express terms to be found in the Outcome Document links the Security Council’s existing authority to act to restore ‘international peace and security’ to a broader understanding of what disturbs international peace:
139. The international community, through the United Nations, also has the responsibility to use appropriate diplomatic, humanitarian and other peaceful means, in accordance with Chapters VI and VIII of the Charter, to help to protect populations from genocide, war crimes, ethnic cleansing and crimes against humanity. In this context, we are prepared to take collective action, in a timely and decisive manner, through the Security Council, in accordance with the Charter, including Chapter VII, on a case-by-case basis and in cooperation with relevant regional organizations as appropriate, should peaceful means be inadequate and national authorities are manifestly failing to protect their populations.
The Security Council has long acted with the understanding that its mandate to take measures to restore international peace and security covers humanitarian crises. The Outcome Document confirms this in Paragraph 139.Footnote 69
Otherwise, the Outcome Document generally supports the terms of the Charter as adopted. Four years later, however, in 2009, the Secretary-General introduced some uncertainty respecting the scope of Member State rights to use force without Security Council authorisation. In his Report on implementing aspects of the World Summit Outcome, Ban Ki-Moon asserted:
When a State refuses to accept international prevention and protection assistance, commits egregious crimes and violations relating to the responsibility to protect and fails to respond to less coercive measures, it is, in effect, challenging the international community to live up to its own responsibilities under paragraph 139 of the Summit Outcome. Such collective measures could be authorized by the Security Council under Articles 41 or 42 of the Charter, by the General Assembly under the ‘Uniting for peace’ procedure … or by regional or subregional arrangements under Article 53, with the prior authorization of the Security Council.Footnote 70
This formulation suggests the General Assembly may authorise the use of force under the terms of its Uniting for Peace Resolution.Footnote 71 The Secretary-General does not clearly support this position, nor could he do so consistently with the terms of the Charter. Under the Charter, the Security Council alone authorises the use of military force. The General Assembly may recommend action that is already lawful in the area of the use of force, such as coordinating certain types of economic sanctions or organising peacekeeping missions that have been authorised by the Security Council or have the consent of all parties to a conflict. The Charter does not support any wider authority. The Report’s vague reference stands in contrast to the World Summit Outcome Document’s clear confirmation of UN members’ understanding of what the Charter means respecting the use of force. In the years since the Report, the General Assembly has not attempted to authorise force.
More specifically with respect to terrorism and terrorist non-State actors, the General Assembly has consistently reiterated that terrorism is a form of crime, not armed conflict. The General Assembly has had primary responsibility for action against terrorism because of this classification. In a 1 July 2016 resolution adopted in connection with a review of the UN’s counter-terrorism efforts, the only reference to the use of military force is this provision, in which the General Assembly,
21. Urges Member States to ensure that any measures taken or means employed to counter terrorism, including the use of remotely piloted aircraft, comply with their obligations under international law, including the Charter, human rights law and international humanitarian law, in particular the principles of distinction and proportionality.Footnote 72
The focus of the General Assembly has been on law enforcement efforts, cooperation among States, education, and ending the financing of terrorist groups. The attempt to adopt a comprehensive treaty against terrorism along these lines has not yet succeeded owing to disagreement over the definition of terrorism, not on the effective ways of countering it.Footnote 73 Some member States do not want violent acts of national liberation groups to count as terrorism. Despite this persistent disagreement, the approach to terrorism has a high level of consensus. The 2016 resolution stresses ‘that a national criminal justice system based on respect for human rights and the rule of law, due process and fair trial guarantees is one of the best means for effectively countering terrorism and ensuring accountability’.Footnote 74
2. The International Court of Justice
The UN General Assembly’s most important resolutions relevant to the use of force, the Declaration on Friendly Relations and the Definition of Aggression, support the Charter’s terms based on the meaning intended in 1945. During the committee and plenary debates to draft the resolutions, member States tended to stress the original understanding of the Charter as drafted, not examples of State practice or other arguments to justify new meanings for terms. The ICJ has taken the same approach in use of force cases with one apparent exception. In the Nicaragua case, the ICJ did delve into what it called State practice.Footnote 75 Yet, the important examples of practice it relied upon turned out to be the same General Assembly resolutions that sought an authentic understanding of terms rather than reviewing the practice of States following the adoption of the Charter in 1945. Beyond the resolutions, the Court looked to condemnation of violations of the Charter, an approach consistent with the Charter prohibition on the use of force having a status beyond customary international law. It also restated the view of the International Law Commission as well as the two parties to the case that Article 2(4) is a peremptory norm.Footnote 76
The ICJ’s first judgment involving the use of force by States was Corfu Channel, decided in 1948.Footnote 77 Albanian shore batteries had fired on British naval vessels navigating through the channel formed by the Island of Corfu and the Greek and Albanian coasts. When the British navigated through the channel again to assert its right to do so, its ships struck marine mines. The British then sent minesweepers to collect evidence for the case it brought against Albania at the ICJ. The Court found that both Albania and the UK violated international law in the incident. The Court found no violation of Article 2(4). The forceful actions involved were presumably below the Article 2(4) threshold. Albania violated the UK right, which existed in 1948, to traverse the channel. Albania also owed the UK a duty under principles of humanity to warn of the marine mines. The UK, on the other hand, had violated Albania’s sovereignty by sweeping for mines, regardless of the purpose, without Albania’s consent. ‘Between independent States, respect for territorial sovereignty is an essential foundation of international relations. … [T]he Court must declare that the action of the British Navy constituted a violation of Albanian sovereignty.’Footnote 78
In 1986, the Court delivered its judgment in the Nicaragua case, which was its first involving a violation of Article 2(4) and a claim to self-defence.Footnote 79 The judgment affirmed that self-defence is an inherent or natural right of States,Footnote 80 but also one to ‘be regarded as limited and legitimated by law’, in particular by the terms of Article 51 itself.Footnote 81 The Court has subsequently confirmed these statements in Nuclear Weapons,Footnote 82 Oil Platforms,Footnote 83 The WallFootnote 84 and Congo.Footnote 85
a) The Classification of Self-Defence
In Nicaragua, the Court could not apply the Charter directly because the US had made a reservation to the ICJ’s jurisdiction that restricted consideration of certain treaties. The Court undertook to find the law of self-defence in customary international law but in a way that was compatible with discerning it to also be a peremptory norm. It observed:
Article 2, paragraph 4, of the Charter of the United Nations … is frequently referred to in statements by State representatives as being not only a principle of customary international law but also a fundamental or cardinal principle of such law. The International Law Commission, … expressed the view that ‘the law of the Charter concerning the prohibition of the use of force in itself constitutes a conspicuous example of a rule in international law having the character of jus cogens’ … The United States, in its Counter-Memorial on the questions of jurisdiction and admissibility, found it material to quote the views of scholars that this principle is a ‘universal norm’, a ‘universal international law’, a ‘universally recognized principle of international law’, and a ‘principle of jus cogens’.Footnote 86
The Court did not explain the method to be used with respect to identifying peremptory norms. The Court’s methodological focus was rather on the development of customary international law.Footnote 87 Alexander Orakhelashvili suggests that the method for finding a peremptory norm is basically the same as that used to find a rule of custom, but that the evidence of practice must be stronger and the opinio iuris must relate to the status of ius cogens.Footnote 88 The Nicaragua judgment is in his view compatible with the finding that Articles 2(4) and 51 form a rule that is both ius cogens and customary international law.Footnote 89 Section III will discuss the methodology indicated in international law for identifying ius cogens. For present purposes, suffice it to say that peremptory norms are distinctive from rules of customary international law. They are not a category of ‘super’ custom. Some ius cogens norms may have insufficient affirmative State practice to qualify as customary international law, and, yet, they are still binding. The ICJ found plenty of evidence that Articles 2(4) and 51 fit the definition of customary international law in addition to being ius cogens. The Court could have also made clear that while customary rules may change with changing State practice, peremptory norms do not. The US reservation, however, only required the Court to apply customary international law. That is all it had to do in Nicaragua, and all it did do.Footnote 90
What the Court did not do was set out a method for undermining the Charter prohibition on the use of force by finding State practice and opinio iuris contrary to Articles 2(4) and 51. Yet, ever since the Nicaragua decision, those who want a weaker prohibition on the use of force have sought to show that contrary practice has modified the Charter. Perhaps the most popular such claim is that, owing to State practice, certain conditions found in or associated with Article 51 are no longer required.Footnote 91 This approach reflects a fundamental misunderstanding of the Nicaragua decision, which the Court could have prevented by clarifying the nature of ius cogens in the text of the decision.
b) The Conditions of Lawful Self-Defence: Significant Armed Attack; Necessity, Proportionality and Attribution
The Court did, however, affirm the armed attack requirement as the sine qua non of self-defence. It clarified that the armed attack of Article 51 must be significant to trigger the right of a defending State to counter-attack on the territory of another State. Minor uses of force, including minor armed attacks, will not give rise to the right of self-defence.Footnote 92 In the jurisdictional phase of the case, the United States argued that Nicaragua had attacked El Salvador by supplying weapons to rebels fighting El Salvador’s government. The US argued it had joined in collective self-defence with El Salvador in defending against these shipments, which the US characterised as constituting armed attacks. The ICJ found that to constitute an armed attack in the legal sense the conduct in question must be more serious than a ‘mere frontier incident’, and that the delivery of weapons would not constitute an armed attack:
The Court sees no reason to deny that, in customary law, the prohibition of armed attacks may apply to the sending by a State of armed bands to the territory of another State, if such an operation, because of its scale and effects, would have been classified as an armed attack rather than as a mere frontier incident had it been carried out by regular armed forces. But the Court does not believe that the concept of ‘armed attack’ includes not only acts by armed bands where such acts occur on a significant scale but also assistance to rebels in the form of the provision of weapons or logistical or other support. Such assistance may be regarded as a threat or use of force, or amount to intervention in the internal or external affairs of other States.Footnote 93
In a later passage, the Court states more directly that it excludes weapons shipments and the provision of supplies from the armed attack category: ‘[T]he Court has indicated that while the concept of an armed attack includes the despatch by one State of armed bands into the territory of another State, the supply of arms and other support to such bands cannot be equated with armed attack.’Footnote 94
In the absence of a significant armed attack (when a use of force is minor), a State may respond with counter-measures but not armed force in self-defence. Countermeasures are otherwise unlawful coercive measures short of armed force.Footnote 95 The ICJ devoted only two of fifteen separate findings in the Nicaragua case to US violations of the prohibition on the use of armed force. These findings cited action that resulted in material damage, injury and death. The Court characterised US interference with Nicaragua’s airspace by overflight of military planes to have been a violation of Nicaraguan sovereignty, but not a violation of the prohibition on the use of force.Footnote 96 Nicaragua’s supply of weapons to armed groups fighting to overthrow the government of El Salvador were also examples of unlawful intervention, not armed attack. These findings support the conclusion that economic, cyber and other types of coercive measures that do not have direct kinetic effects are unlikely to constitute the use of armed force as prohibited in Article 2(4). States may respond to attacks in the non-kinetic category with counter-measures, not military force, per Nicaragua.Footnote 97
The ICJ also inquired in Nicaragua into the meaning of the term ‘inherent right’ in Article 51. The Court explained that the ‘inherent right’ of self-defence is referring to the set of rules and principles both within and beyond the Charter. Articles 2(4) and 51 provide the lawful bases for resort to force as well as certain procedural rules, such as the Article 51 requirement that States using force in self-defence must report to the Security Council. The principles of State responsibility such as attribution, as well as the principles of necessity and proportionality and other conditions on the lawful resort to force, make up the ‘inherent right’. In the jurisdiction phase of the case, the ICJ referenced ‘principles of customary and general international law’ that exist alongside treaties. The ICJ provided the examples of non-intervention and respect for the independence and territorial integrity of States.Footnote 98 In the merits phase, the Court went on to say,
On one essential point, this treaty [the Charter] itself refers to pre-existing customary international law; this reference to customary law is contained in the actual text of Article 51, which mentions the ‘inherent right’ (in the French text the ‘droit naturel’) of individual or collective self-defence, which ‘nothing in the present Charter shall impair’ and which applies in the event of an armed attack. The Court therefore finds that Article 51 of the Charter is only meaningful on the basis that there is a ‘natural’ or ‘inherent’ right of self-defence … Moreover the Charter, having itself recognized the existence of this right, does not go on to regulate directly all aspects of its content. For example, it does not contain any specific rule whereby self-defence would warrant only measures which are proportional to the armed attack and necessary to respond to it.Footnote 99
Necessity and proportionality are best categorised as part of general international law, rather than customary international law.Footnote 100 As general law or general principles, they have much in common with peremptory norms. They do not change in the same manner as treaties or customary international law rules. They have a stable and timeless quality that is at odds with arguments to permit greater resort to lawful force. The nature of these principles and their importance to the functioning of any legal system will be discussed further in Section III.
The ICJ did not need to reach issues of necessity, proportionality or attribution with respect to the US use of military force against Nicaragua because no significant use of force and hence no armed attack was proven:
Since the Court has found that the condition sine qua non [armed attack] required for the exercise of the right of collective self-defence by the United States is not fulfilled in this case, the appraisal of the United States activities in relation to the criteria of necessity and proportionality takes on a different significance. As a result of this conclusion of the Court, even if the United States activities in question had been carried on in strict compliance with the canons of necessity and proportionality, they would not thereby become lawful.Footnote 101
The Court did not comment on the history or nature of the requirement of attribution, but found the US not responsible for the human rights violations of a non-State actor armed group, the Contras, because the US did not control them.Footnote 102
The US did violate the principle of non-intervention in some of its actions against Nicaragua, including financing and advising the Contras. The ICJ also referred to the Declaration on Friendly Relations comment on the principle of non-intervention and its example that State-sponsored terrorist attacks on the territory of another State violate non-intervention.Footnote 103 This passage in the judgment is a reminder that States need not stretch Article 51 to fit cases beyond those involving significant armed attack. International law also has such principles as non-intervention to govern inter-State conduct.
In the 1996 Nuclear Weapons advisory opinion, the ICJ returned to the general principles of necessity and proportionality again in the context of self-defence: ‘[T]here is a specific rule whereby self-defence would warrant only measures which are proportional to the armed attack and necessary to respond to it, a rule well established in customary international law.’Footnote 104 The Court referred to necessity and proportionality as customary international law but with no reasoning to support that categorisation. As with peremptory norms, the ICJ has been hesitant about the category of general principles. In the Nuclear Weapons opinion, the Court seemed to default to customary rules simply because necessity and proportionality are not treaty rules.
Regardless of this methodological weakness in reference to necessity and proportionality, the ICJ was right to emphasise that the principles are critical to the law of self-defence. Necessity and proportionality provide additional support for the conclusion that the Article 51 conditions cannot as a practical matter be read out of the Charter. Unless an actual attack is in evidence, the State planning to respond will be unable to accurately calculate whether force in self-defence is needed, whether it will succeed or whether it will be proportionate. In such a situation, the defending State is engaging in lethal action based on mere guesses respecting the actual use of force. In the killing of Khan and Hussain (the ISIS members mentioned at the beginning of this chapter), their future plots were hypothetical and as such inadequate to assess the requirements of necessity and proportionality. Equally, a hypothetical attack cannot meet the additional requirement that an initial attack must be sufficiently grave or significant to trigger the right of self-defence. The requirement of gravity hinges on the attack being significant in reality. It is not enough to guess that an attack will occur and to further guess that it will be sufficiently serious.
In two subsequent cases, the ICJ again emphasised both the need for the triggering attack to be significant and attributable to the State against which force in self-defence is being exercised. In the 2003 Oil Platforms case, the Court held:
[I]n order to establish that it was legally justified in attacking the Iranian platforms in exercise of the right of individual self-defence, the United States has to show that attacks had been made upon it for which Iran was responsible; and that those attacks were of such a nature as to be qualified as ‘armed attacks’ within the meaning of that expression in Article 51 of the United Nations Charter, and as understood in customary law on the use of force. As the Court observed in the case concerning Military and Paramilitary Activities in and against Nicaragua, it is necessary to distinguish ‘the most grave forms of the use of force (those constituting an armed attack) from other less grave forms.’ … ‘In the case of individual self-defence, the exercise of this right is subject to the State concerned having been the victim of an armed attack’.Footnote 105
The ICJ also relied on the principle of attribution in The Wall advisory opinion.Footnote 106 The case arose from a General Assembly request for an opinion on the legality and consequences of illegality of the security barrier or wall that Israel has constructed at some points within the Occupied Palestinian Territories (OPT). Israel took the position that the structure within the OPT is justified as an exercise of its right of self-defence under Article 51.Footnote 107 The Court, however, said Article 51 was not relevant to the case. Israel, as the occupying power, exercises control over the OPT.Footnote 108 Invoking Article 51 in such a case would be analogous to a government invoking Article 51 in responding to a high level of violence by a non-State actor on its own territory. Only when the violence reached a level of armed conflict and Israel no longer exercised the control necessary to qualify as an occupier would there be a reasonable case for invoking Article 51.
In her often-cited separate opinion in the case, Judge Rosalyn Higgins argued that Article 51 makes no mention that the armed attack requirement means an armed attack by a sovereign State.Footnote 109 While this statement is correct, Higgins did not disagree with the conclusion of the majority that Israel is the occupying power in the OPT.Footnote 110 Her separate opinion, therefore, includes an implicit contradiction. An occupier is in control of territory. It is a situation analogous to a government’s relation to its own territory. When a State uses force against an uprising, it does not invoke Article 51. For Article 51 to be relevant, Israel must have lost control of the OPT, which Higgins acknowledges was not the case.
The ICJ discussed loss of control in the 2005 Congo case. There the Court said that attacks on Uganda by non-State actors located in Congo but outside the control of Congo did not trigger Article 51 self-defence by Uganda against its neighbour. The Court added that this was not a case where a ‘large-scale attack’ on Uganda emanated from Congolese territory.Footnote 111 The Court’s comment is brief but implies that where a State is not responsible for a non-State actor, that actor must itself control enough territory to have the capacity to launch a large-scale attack. In such a situation Article 51 may be relevant to self-defence against a non-State actor.
In occupation law and the law of self-defence, the relevant concept is ‘control’, as the ICJ held in the Nicaragua case and Bosnia v. Serbia, and implied in Congo. Where a State wishes to use force in self-defence following an attack by a non-State actor, the defending State must establish that the State where the counter-attack will occur controlled the non-State actor,Footnote 112 or had lost control of territory so that the non-State actor could mount ‘large-scale’ attacks. The ICJ underscored this point in the Congo case. The Court rejected Uganda’s argument that attacks by irregular forces not attributable to Congo triggered Uganda’s right to use force on Congolese territory.Footnote 113
Judges Simma and Kooijmans disagreed. They argued that a State acting in self-defence may carry out an attack on the territory of a State regardless of the host State’s responsibility for a non-State actor.Footnote 114 Their position, however, fails to account for the rights of the host State where a defending State inflicts death, destruction and injury. The ICJ majority made it clear in Congo and Oil Platforms that self-defence is lawful only against a State proven to bear responsibility for an unlawful armed attack.Footnote 115 The territorial State may have failed to exercise due diligence with respect to controlling non-State actors, but failure of due diligence does not in itself give rise to another State’s right to use force in self-defence. This is a point of law that the ICJ has emphasised in most of its cases on the use of force.Footnote 116
c) Intervention by Invitation
These conclusions on the importance of attribution are further supported in judgments respecting intervention by invitation. The ICJ has discussed invitation as a distinctive basis for justifying the use of force on another State’s territory when strict conditions are met. In the Congo case, the DRC government issued invitations to neighbouring States to assist it in defeating insurgent forces. The Charter says nothing about the legality of participation in internal armed conflict. Article 51 permits joining in collective self-defence at the invitation of a State. If invitation to civil war is permissible under international law, then some of the restrictions on a State joining in collective self-defence may apply directly or indirectly. One restriction that likely applies is that an invitation must be public and express. The ICJ indicated the importance of proof of invitations in the Nicaragua case where the US lacked evidence of an invitation by El Salvador to join in self-defence against Nicaragua.Footnote 117
Without consent, military activities on the territory of another State will violate the principle of non-intervention or the prohibition on the use of force. Consent precludes such wrongfulness, to use the language of the International Law Commission in the Articles on State Responsibility. Consent is not so much customary international law as a general principle of law. As such, the particulars are not necessarily found in State practice and opinio iuris but in logic and the necessity of the legal system. According to the commentary on the Articles on State Responsibility, consent to forego a right as a general matter must ‘be freely given and clearly established. It must be actually expressed by the State rather than merely presumed on the basis that the State would have consented if it had been asked.’Footnote 118 Consent must be given by the ‘legitimate’ government,Footnote 119 signalled by effective exercise of governmental authorityFootnote 120 or control ‘through internal processes’.Footnote 121 Where a government that has been exercising effective control is fighting a civil war, it retains its position as the legitimate government so long as it has a chance of winning.Footnote 122
In Congo, the ICJ found that consent must be ‘unequivocally implied from the conduct of the State’.Footnote 123 Withdrawing consent requires no formal, express evidence. Indirect evidence suffices. This finding is consistent with the position that a high bar exists to the lawful exercise of armed force on a foreign State’s territory under a justification of invitation or consent. Indirect and even ambiguous evidence of withdrawal of consent is sufficient to end it. Decades ago, Louise Doswald-Beck pointed to the concerns of many States that intervention on either side of a civil war interferes with self-determination.Footnote 124 In most cases, such intervention also leads to escalation in violence. If international law develops in the direction of further restrictions on the use of force, intervention by invitation could come to be understood as a violation of the Charter. At present, the weight of opinion, including the ICJ’s implied view in Congo and the Nicaragua case, is that invitation is a lawful basis for the use of force abroad but only when issued by a government generally in control.Footnote 125 When a non-State actor seeks to replace a government in all or part of a State’s territory, the existing government remains the government until the non-State actor reaches the point at which it will likely succeed in taking control.Footnote 126
Intervention by the invitation of either side in a civil war conflicts with self-determination. It also conflicts with the right to life, a norm some consider to be ius cogens.Footnote 127 The United Nations International Covenant on Civil and Political Rights, drafted through the General Assembly, declares in Article 6:
Every human being has the inherent right to life. This right shall be protected by law. No one shall be arbitrarily deprived of his right to life.Footnote 128
Article 6 renders every first use of military force lacking a Security Council authorisation unlawful. The initiator of military force will almost inevitably violate the human right to life. Non-State actor group members who initiate killing are committing murder. Government authorities have the right to use force to protect a life immediately. Force used in excess of that limit will also constitute murder.Footnote 129 Despite these principles, governments and non-State actors may engage in fighting that escalates beyond crime to armed conflict. At that point, international humanitarian law (IHL) becomes relevant to protecting the right to life. Parties to an armed conflict will violate Article 6 if they do not comply with relevant IHL.Footnote 130
Outside of armed conflict, the United Nations Basic Principles for the Use of Force and Firearms by Law Enforcement Officials (UN Basic Principles), which are widely adopted by police throughout the world, provide in Article 9:
Law enforcement officials shall not use firearms against persons except in self-defence or defence of others against the imminent threat of death or serious injury, to prevent the perpetration of a particularly serious crime involving grave threat to life, to arrest a person presenting such a danger and resisting their authority, or to prevent his or her escape, and only when less extreme means are insufficient to achieve these objectives. In any event, intentional lethal use of firearms may only be made when strictly unavoidable in order to protect life.Footnote 131
In considering the legality of using force in self-defence, the ICJ relies generally on the terms of the Charter, the general principles of law, and its own past decisions. The Nicaragua case may seem to be an outlier because of the reliance on customary international law. Even in Nicaragua, however, the Court used resolutions and declarations of the United Nations and condemnations of State practice involving the use of force to confirm that customary international law and even ius cogens mirrored the Charter as drafted in 1945.
3. Security Council
As with the other UN organs, the over seventy-year history of Security Council action indicates a consistent understanding that the right of self-defence is highly restricted. The right reflects Article 51’s plain terms. During the Cold War, the Security Council paid scant attention to the problem of terrorism. Since 9/11, however, the Council has played a larger role. That role will be discussed briefly here, but several non-terrorism related incidents will also be considered. These incidents are worth considering as several have figured prominently in arguments to expand the right to use force. The Security Council, unlike the expansionists, has generally remained close to the Charter’s terms in carrying out its mandate as the debates and resolutions concerning Korea (1950), Suez (1956), Cuba (1962), Osirak (1981), Kuwait (1990–1), Kosovo (1999), 9/11 (2001), Iraq (2003), Libya (2011), Syria (2012–) and terrorist attacks in Europe, the Middle East and North Africa indicate.
While leaving terrorism to the General Assembly for most of its history, the Security Council did adopt a resolution in its first years condemning the assassination of the UN mediator in the Arab–Israeli conflict, Count Folke Bernadotte by ‘a criminal group of terrorists’ – the Lehi, a pro-Israel, non-State actor armed group.Footnote 132 The Council did not pass another resolution on terrorism until 1970.Footnote 133 This record is further confirmation that at the UN terrorism has, since the founding, been categorised as an issue of crime, not military force.
An early crisis involved the Korean peninsula. At the end of the Second World War in the Pacific, the United States and the Soviet Union competed to replace Japan as it withdrew from conquered territory following its sudden, unconditional surrender. American military staff believed the US was in a position to hold Korea on behalf of the United Nations but only south of the thirty-eighth parallel. The Soviet Union brought its influence to bear on the north. This situation prevailed until June 1950, when the Soviet Union, enlisting the help of the new Chinese communist leadership, induced North Korea to attack the South in a bid to reunite the country.Footnote 134 On news of the attack, the United States requested that the Security Council allow it to lead a United Nations counter-attack. The Soviet Union was boycotting Security Council deliberations at the time to protest the refusal to transfer China’s seat from the government on Taiwan to the new communist government. The Korea resolutions passed.Footnote 135 The war that ensued continued until 1953 when an armistice re-established the de facto border at the thirty-eighth parallel. For the international law on the use of force, the Korean War is important as confirming the role of the Security Council in responding to uses of force beyond Article 51 self-defence. The Korean War was not an inter-State war of self-defence.Footnote 136 The Soviet Union and subsequently Russia never boycotted Security Council meetings again, helping to solidify the Council’s central role in peace and security.
Once the Soviet Union returned to the Council, the United States tried to open an alternative avenue for authorising the use of force outside the Security Council by sponsoring the Uniting for Peace Resolution in the UN General Assembly.Footnote 137 The Uniting for Peace Resolution has been invoked several times, including in the Suez Crisis. As already mentioned, the General Assembly has no authority to authorise force.Footnote 138
The Suez Crisis raised the issue of self-defence under the Charter front and centre. Tensions in the Middle East erupted into armed conflict following Egypt’s nationalisation of the Suez Canal on 26 July 1956. The Canal had been owned by a British–French consortium. After attempts to get the UN involved on their behalf, France, Israel and the United Kingdom developed an extraordinary plan for retaking the Canal in which Israel would attack Egypt, then France and the UK would intervene between the two warring States to restore order.Footnote 139 During the intervention, French and British forces would wrest control of the Canal away from Egypt. Israel duly attacked on the night of 29 October. On 30 October, the US called an emergency session of the Security Council. During the session, France and the UK issued an ultimatum to Egypt and Israel to cease fire and withdraw ten miles from the Canal area. France and the UK vetoed other proposals for a ceasefire. On 31 October, after announcing that Egypt had rejected their ultimatum, France and the UK intervened. A meeting of the General Assembly under the Uniting for Peace Resolution was convened and organised the United Nations Emergency Force to enforce a ceasefire.Footnote 140 France and the UK withdrew their troops by the end of December 1956. Israel withdrew by the end of March 1957.
Israel put forward three arguments based on self-defence to justify its use of force against Egypt. The Israeli representative began by arguing in the Security Council that Israel had taken protective action against the Egyptian Fedayeen, a group that formed to oppose British encroachments on Egyptian sovereignty.Footnote 141 He added that Israel was exercising its ‘inherent right of self-defence’.Footnote 142 In the Emergency Special Session of the General Assembly, Israel’s delegation asserted that while no single attack from Egypt triggered Israel’s right of self-defence, an accumulation of ‘encroachments’ did.Footnote 143 In other words, ‘Israel relied on a broad interpretation of Article 51.’Footnote 144 It was certainly a flexible reading of the attribution requirement. The interpretation was clearly rejected in a General Assembly resolution disapproving of Israel’s use of force by sixty-four votes to five with six abstentions out of a total UN membership at the time of seventy-six.Footnote 145 In addition, various representatives criticised the lack of necessity for the use of force and for its disproportion. Alexandra Hofer observes that the most consistent critique among UN member States was of Israel’s methods, which ‘exceeded what the situation required’.Footnote 146 The US Secretary of State, John Foster Dulles, speaking to the General Assembly, said of the Fedayeen encroachments that ‘these provocations – serious as they were – cannot justify the resort to armed force which has occurred during these last two or three days and which is continuing tonight.’Footnote 147
The British and French made a series of arguments of their own to try to justify their counter-intervention: they claimed they were enforcing the Armistice Agreement between Egypt and Israel; they wanted to guarantee freedom of navigation in the canal; they were acting because the Security Council had proven itself unable to do so; their action was a mere ‘police action’ outside the scope of the Charter;Footnote 148 and they were protecting their nationals abroad.Footnote 149 During confidential cabinet discussions British Prime Minister Anthony Eden also expressed the view that it was justifiable to use force to secure vital national interests.Footnote 150 He had, however, been advised by the head of the British Foreign Office Legal Department, Gerald Fitzmaurice, that attacking Egypt to re-take the Canal would be ‘a clear illegality and breach of the United Nations Charter’.Footnote 151 The United States and the Soviet Union took the same position.
It was a brief moment of superpower unity. In 1962 the US discovered a Soviet plan to locate missiles on Cuba with the capacity to reach the United States. Some Kennedy administration officials strongly urged bombing the missile sites and the ships delivering rockets.Footnote 152 Such a first use of force would clearly violate Article 2(4). President Kennedy’s brother, Robert, compared such an attack with Japan’s attack on Pearl Harbor, Hawaii.Footnote 153 The Soviet Ambassador to the United States, Anatoly Dobrynin, would later write that ‘[t]hose days revealed the mortal danger of a direct armed confrontation of the two great powers, a confrontation headed off on the brink of war thanks to both sides.’Footnote 154
Instead of attacking, the US sought to interdict the ships by imposing a naval blockade, which it called a ‘quarantine’ since a ‘blockade’ had long been considered a casus belli.Footnote 155 Regardless of the label, State Department lawyers advised that it would violate the Charter unless authorised by the Security Council, which was a non-starter due to the guaranteed Soviet veto. The US went instead to the Organisation of American States (OAS).Footnote 156 The OAS had no authority to authorise a use of force in the absence of an armed attack,Footnote 157 but US officials believed the move gave some recognition of restraint in using force out of respect for the law.Footnote 158 The only other idea was to argue that the placement of weapons in Cuba constituted an armed attack for purposes of Article 51.Footnote 159 Apparently, there was real concern about establishing an expansive interpretation of the phrase ‘if an armed attack occurs’.Footnote 160 In the end, the US quarantine did not materialise into a use of force because Khrushchev ordered Soviet ships to reverse course rather than confront the US ships. The crisis was resolved when the Soviet Union agreed not to place missiles on Cuba in exchange for a secret promise by the US to withdraw its missiles from Turkey.
The Security Council’s most important debate on self-defence was likely the multi-day session held following Israel’s 7 June 1981 attack on a nuclear reactor under construction at Osirak, Iraq. Israeli Prime Minister Menachem Begin justified the raid citing Israeli intelligence reports that the reactor could go into operation as early as 1 July 1981.Footnote 161 The International Atomic Energy Agency (IAEA), however, intended, once the reactor became operational, to place full-time inspectors in Iraq ‘which would have made any plutonium production impossible’.Footnote 162 Iraq was a State party to the Nuclear Non-Proliferation Treaty and its nuclear installations were inspected on a regular basis by the IAEA.Footnote 163 Israel was determined to thwart any nuclear activity in Iraq, but its air attack was almost universally condemned as an act of aggression.Footnote 164 At the Security Council, Israel argued it was justified in attacking Iraqi nuclear facilities to halt a potentially ‘fatal process before it reaches completion’.Footnote 165 The Security Council in Resolution 487 nevertheless condemned the Israeli action as a pre-emptive attack on the Osirak ‘in clear violation of … the norms of international conduct’ and ‘a serious threat to the entire safeguards regime of the [IAEA and of the NPT]’.Footnote 166 Even the US voted against Israel. Resolution 487 passed unanimously. The US Permanent Representative to the UN, Jeane Kirkpatrick, observed that ‘the means Israel chose to quiet its fears about the purposes of Iraq’s nuclear programme have hurt, and not helped, the peace and security of the area … Israeli action has damaged the regional confidence that is essential for the peace process to go forward.’Footnote 167
Despite this rejection of Israel’s expansive claim to a right of self-defence to pre-empt a hypothetical future attack, Israel continued to assert broad claims of lawful self-defence, especially against non-State actor attacks from Lebanon, Jordan and Tunisia. In 1982, Israel invaded Lebanon, advancing as far as the capital, Beirut – well beyond the area where attacks on Israel originated. Israel remained in Lebanon for three-and-a-half months. The United States supported Israel’s right of self-defence in these incidents, but criticised the actual use of force as disproportionate.Footnote 168
In 1985, Israel attacked the PLO headquarters in Tunis in response to attacks by PLO members in Israel. Israel again raised as justification its right of self-defence and Tunisia’s failure to control terrorists on its territory. The Security Council was not persuaded that Tunisia was legally responsible for the PLO’s violence against Israel or that Israel’s response was proportionate. The Council condemned ‘vigorously the act of armed aggression perpetrated by Israel against Tunisian territory’ by a vote of fourteen to zero, with the US abstaining.Footnote 169 The Council also condemned the PLO for violence in its struggle with Israel, finding no justification for the PLO’s methods in the right of self-determination.
Throughout the 1980s and 1990s, the Security Council became more involved in terrorism suppression. In 1999, after imposing sanctions on Afghanistan to pressure it to hand over Al-Qaeda’s leader, Osama bin Laden, the Council adopted Resolution 1269 condemning ‘all acts, methods and practices of terrorism as criminal and unjustifiable, regardless of their motivation’.Footnote 170 The attacks of 9/11 did mark a departure, however. The Security Council cited the terms of Article 51 (‘inherent right of self-defence’) in its immediate post-9/11 resolutions, although only in the non-operative parts.Footnote 171 The Council did not authorise the use of force or make findings with respect to any of the other conditions of lawful self-defence. Critically, the Council said nothing about attribution, necessity or proportionality. In a subsequent comprehensive resolution (Resolution 2249) in the aftermath of attacks in five cities during 2015, the Council used its typical formulation for authorising the use of force (‘all necessary means’) but linked those terms to ISIS control of Iraqi and Syrian territory. The Council did not cite Chapter VII as the legal basis of the resolution but referred more generally to member States’ obligations to act in compliance with international law. Most of Resolution 2249 emphasises the need for solidarity against terrorism.Footnote 172 No reference is made to Article 51. Nevertheless, expansionists have tried to use resolutions like 1368, 1373 and 2249 to support their arguments for the legality of using military force against terrorist suspects regardless of the responsibility of the State where they are found.Footnote 173
The Security Council pattern is remarkably consistent with that of the General Assembly and ICJ. Each UN organ has reflected an understanding of the Charter principles on use of force aligned with the plain terms of the text and the drafters’ intentions. The often-cited exception is Security Council Resolution 1368, which mentions Article 51 in the aftermath of a non-State actor attack.Footnote 174 Such an example would not alter even legal principles subject to change through subsequent practice.
III. Three Pernicious Doctrines of Expansive Self-Defence
The law’s durability is linked to the normative underpinnings of the prohibition on the use of force. Despite them, scholars have persisted in challenging the prohibition. Three prominent challenges are discussed in this section. They are presented chronologically. Each was introduced as a post hoc justification for a government’s policy of force. All three have been influential, but they also conflict with the peremptory status of the prohibition on the use of force. The conflict with ius cogens is the most significant issue, but the doctrines suffer from other flaws as well.
The doctrines consist of, first, the assertion of a right to use force in self-defence against imminent or threatened attacks based on the term ‘inherent right’ in Article 51. The second characterises crimes committed by terrorists as the equivalent of armed attacks or armed conflict. It also asserts that many small incidents can be accumulated to reach the significance threshold for the armed attack requirement of Article 51. The third asserts that where a State is ‘unable or unwilling’ to control terrorism, the legal requirements of attribution or consent no longer apply.
Bowett presented the first idea in 1958 in the aftermath of the Suez Crisis. He drew liberally on the Caroline incident to assert that the ‘inherent right of self-defence’ of States includes a right to use force in the face of necessity and not only ‘if an armed attack occurs’.Footnote 175 His argument has heavily influenced the debate around self-defence. Jeremy Wright, UK Attorney General, for example, re-stated the Bowett thesis in January 2017, as constituting the UK understanding of the ‘modern’ law on self-defence.Footnote 176 The second perspective is associated with Judge Sir Christopher Greenwood’s support of a United States claim that terrorist crime can amount to armed attack under Article 51.Footnote 177 Sir Daniel Bethlehem, a former legal adviser to the British Foreign and Commonwealth Office, made the third proposal following a decade of US targeted killing operations against non-State actors using military force outside armed conflict zones and without a showing that acts of the non-State actor could be attributed to the host State.Footnote 178 These attempts to broaden the scope of the right to self-defence are – to borrow Henkin’s label for Bowett’s argument – ‘pernicious doctrines’ of self-defence. By ‘pernicious’ Henkin meant the proposition has had a persistent, negative influence on the prohibition on the use of force. Why these doctrines persist despite their legal defects would require a sociological enquiry. They do reflect a contemporary faith in the utility of military force and take as a given that politicians will ignore the law unless it supports their policies.Footnote 179 These power-related factors should not, in principle, influence legal analysis. Regardless of formal doctrine, diluting rules to please politicians only destroys the law in the attempt to save it.
Henkin firmly rejected attempts to dilute the Charter. He did so out of personal knowledge and experience. He had been a lawyer for the United States government dealing with international law issues. He had also been a soldier. Henkin won the Silver Star for valour on the battlefield during the Second World War. Nevertheless, he staunchly repudiated inflated views of the utility of military force and attempts to weaken the legal prohibition against it. He was also a man of faith and deep moral conviction. He said of efforts to expand the right to use military force:
It is not in the interest of the United States to re-construe the law of the Charter so as to dilute and confuse its normative prohibitions … [I]t is important that Charter norms – which go to the heart of international order and implicate war and peace in the nuclear age – be clear, sharp, and comprehensive; as independent as possible of judgments of degree and of issues of fact; as invulnerable as can be to self-serving interpretations and to temptations to conceal, distort, or mischaracterize events.Footnote 180
A. Inherent/Imminent
Bowett introduced his idea that the ‘inherent right’ of self-defence permits a State to attack in the absence of an armed attack occurring just fourteen years after the adoption of the Charter. More relevantly, he introduced it just two years after the ill-fated attempt by Britain and France to regain control of the Suez Canal. Bowett wrote in the preface to his 1958 book, Self-Defence in International Law, that Suez had a ‘considerable impact’ on his writing of the book.Footnote 181 When the truth emerged of the pre-arranged plan to have Israel attack Egypt to create a pretence for British and French intervention, France and Britain fell back on claims of self-defence. Standing in the way of these claims was the UN Charter’s Article 51 with its requirement of an armed attack. Bowett, however, supported his government’s self-defence claims by attacking the terms of Article 51, saying, ‘there is no explanation of this curious proviso “if an armed attack occurs”.’Footnote 182 States, he asserted, retained a right to act in self-defence consistent with the customary international law in place prior to the adoption of the Charter in 1945, as signalled by the reference in Article 51 to an ‘inherent right’ of self-defence. Essentially, in Bowett’s view, States could simply overlook the Article 51 requirement of an armed attack occurring. Bowett also ignored the relationship of Article 51 to the Charter as a whole, the Charter’s drafting history, and discussions to that point in the UN, including on Suez. Bowett moved directly from the words ‘inherent right of self-defence’ back to 1841 and correspondence between British and American officials about the scuttling of the ship Caroline over Niagara Falls.Footnote 183 He contended that customary international law permits the use of armed force in situations of ‘necessity’.Footnote 184 The subsequent impact of Bowett’s use of the Caroline episode is noteworthy. While he failed to reverse the consensus that the UK acted unlawfully in the Suez, he succeeded in raising considerable doubt about the armed attack requirement of Article 51. Since 1958, the Caroline incident has been invoked repeatedly to try to justify uses of force as self-defence that plainly conflict with Article 51.
Ian Brownlie, another British academic, provided a point-by-point refutation of Bowett’s thesis in his own 1963 book, International Law and the Use of Force by States. Brownlie warned against the tendency of writers to claim justifications for the use of force found in customary law prior to the 1920s. He singled out for particular criticism attempts to base rights of self-defence on the correspondence over the Caroline incident. Brownlie took a strict position on interpreting Article 51, finding no room for anticipatory self-defence or self-defence under Article 51 to respond to actions not involving armed force. He defended his strict stance, saying, ‘[T]he dominant policy of the law and of the United Nations is to maintain international peace and to avoid creating possibilities of breaches of the peace, in the form of vague and extensive justifications for resort to force …’Footnote 185
Despite Brownlie’s persuasive analysis, certain American legal analysts kept Bowett’s Caroline thesis alive in the 1980s and 1990s. They cited it to justify the use of force in a variety of situations, such as using force in anticipation of a future attack.Footnote 186 Caroline is today being cited most often to justify using force long after a terrorist attack has occurred or in anticipation of a future terrorist attack as a preventive or pre-emptive measure.Footnote 187 In 2004, UK Attorney General Lord Goldsmith spoke in Parliament about his understanding of Article 51:
It is clear that the language of Article 51 was not intended to create a new right of self-defence. Article 51 recognises the inherent right of self-defence that States enjoy under international law. That can be traced back to the ‘Caroline’ incident in 1837 … The Government’s position is supported by the records of the international conference at which the UN Charter was drawn up and by State practice since 1945. It is therefore the Government’s view that international law permits the use of force in self-defence against an imminent attack but does not authorise the use of force to mount a pre-emptive strike against a threat that is more remote. However, those rules must be applied in the context of the particular facts of each case. That is important.
The concept of what constitutes an ‘imminent’ armed attack will develop to meet new circumstances and new threats. For example, the resolutions passed by the Security Council in the wake of 11 September 2001 recognised both that large-scale terrorist action could constitute an armed attack that will give rise to the right of self-defence and that force might, in certain circumstances, be used in self-defence against those who plan and perpetrate such acts and against those harbouring them, if that is necessary to avert further such terrorist acts.Footnote 188
Goldsmith is in error respecting the drafting history of the UN Charter.Footnote 189 As for his reference to the UK government’s long policy, no actual case involving the use of force relying on Bowett’s ‘inherent right’ doctrine is evident between Suez in 1956 and Syria in 2015. One example scholars often cite is the UN Security Council’s failure to clearly condemn Israel for attacking Egypt in the 1967 Six-Day War. The UK was not involved in the Six-Day War. Moreover, it is an equivocal case at best given that Israel argued before the Security Council in 1967 that it had actually been attacked by Egypt prior to responding with the use of force.Footnote 190 Israel did not claim to be anticipating an Egyptian attack. Despite this, the UK Parliamentary joint committee implies, in its report on the UK’s policy with respect to the use of drones in targeted killing, issued following the August 2015 attacks, that international law permits using force in self-defence when an opponent’s attack is ’imminent’.Footnote 191 Goldsmith’s successor, Jeremy Wright, cited the Caroline incident for legal support of a right to use force in the absence of an armed attack in his January 2017 speech.Footnote 192
Goldsmith and Wright go to some trouble to try to limit the potentially open-ended nature of the concept of ‘imminence’ in the ‘inherent right’ doctrine. Goldsmith attempts to show UK policy to be different from the US Bush administration’s asserted right of ‘pre-emptive’ self-defence. Later, Wright tried to distinguish the UK position from that outlined by the Obama administration in which US government lawyers re-defined ‘imminent’ to mean not immediate.Footnote 193 Neither attempt at containing the potential expansion is persuasive. They both conflict with the plain terms of Article 51. Perhaps the UK’s positions are more defensible as a matter of law than those of the US under Bush and Obama. They nevertheless conflict with the prohibition on the use of force.
President George W. Bush first revealed a new US understanding of Article 51 in a speech at the West Point Military Academy in June 2002. He indicated ‘that not only will the United States impose pre-emptive, unilateral military force when and where it chooses, but the nation will also punish those who engage in terror and aggression and will work to impose a universal moral clarity between good and evil’.Footnote 194 Similar statements appeared subsequently in the Secretary of Defence’s 2002 Annual Report to the President and the CongressFootnote 195 and the National Security Strategies of 2002 and 2006.Footnote 196 The 2006 National Security Strategy also stated a claim for the right to use force to pre-empt future attacks.Footnote 197 The terminology may not appeal to UK lawyers, but there is little difference between launching an attack when fearing an attack is imminent, launching an attack in anticipation of an attack, and launching an attack to pre-empt one. In all cases, the attack is launched based on the subjective belief of a future attack, rather than the evidence of an attack occurring.
In 2010, lawyers in the Obama administration provided legal advice generally supporting the Bush administration. In lengthy memos focused on the legality of using military force to target and kill US citizens abroad and outside armed conflict zones, the lawyers concluded ‘imminent’ need not mean ‘immediate’. An individual’s propensities and potential were enough to justify using military force on the territory of another State.Footnote 198 Again, the decision to use force is based on a guess about a future attack. The UK’s Wright recognises the problem of ‘imminent’ having no objective meaning: ‘So one of the real-world legal questions we face today is not so much who threatens an armed attack, but the standards by which we judge whether such an attack is imminent, allowing a lawful response by way of self-defence.’Footnote 199 He adopts Bethlehem’s proposals to supply the needed ‘standards’.Footnote 200 These are the nature and immediacy of the threat; the probability of an attack; whether the anticipated attack is part of a concerted pattern of continuing armed activity; the likely scale of the attack and the injury, loss or damage likely to result therefrom in the absence of mitigating action; and the likelihood that there will be other opportunities to undertake effective action in self-defence that may be expected to cause less serious collateral injury, loss or damage.Footnote 201
These standards are as subjective as the term ‘imminent’. They do not provide meaningful limits on the use of force, even if they were the law. They do not even supply much restraint on the position that ‘imminent’ need not mean ‘immediate’.
Despite the inherent weaknesses of Bowett’s Caroline thesis from a legal and practical perspective, its influence continues to spread. A UN Special Rapporteur on extrajudicial killing, Christof Heyns, characterised Article 51 as recognising ‘the right to self-defence where an armed attack occurs, but also refer[ring] to self-defence as an inherent right of States. This has given rise to arguments that the right to self-defence under customary law is not displaced by the Charter.’Footnote 202 As Heyn’s comment shows, Bowett’s attempt to defend the UK decades ago has evolved to be a persistent and pernicious pattern in Article 51 interpretation. Instead of basing the right to use force on a response to an initial armed attack, the view has been growing that States may use military force to target and kill terrorist suspects who possess the material capacity to perpetrate violence and who have given some indication of willingness to do so.
Pakistani scholar Sikander Ahmed Shah rejects the Bowett view. He, like Brownlie, points out that the Caroline correspondence contains no basis for a right of self-defence that survived the adoption of the UN Charter: ‘[T]he test the US Government is relying on arises out of pre-UN Charter customary international law norms that have long since been refined and restrained by the application of the UN regime …’Footnote 203
B. Terrorism/War
In 1986, the United States justified an attack on Libya that killed over 100 people citing the right of self-defence. The US claimed that Libya was responsible for a series of violent incidents, the most serious of which was the bombing of a disco in Berlin frequented by US armed service personnel, in which two US servicemen and a civilian woman were killed.Footnote 204 The US claimed it also had evidence proving the same attackers were planning more attacks.Footnote 205 US President Ronald Reagan ordered air strikes on military sites in Libya. Ghaddafi, the Libyan leader, had a home at one of the sites. His young daughter was among the people killed in the attack.
Greenwood defended the US attacks under Article 51 of the UN Charter, citing Bowett’s theory of ‘inherent right’. Greenwood expanded Bowett’s position to include the right to respond in self-defence to low level criminal acts that have occurred in the past as evidence they might occur again in the future. Greenwood concluded his analysis as follows:
[T]he air strike against Libya would be justifiable as an exercise of the right of self-defence if, but only if, it satisfied the following conditions:
1. that the air strike was carried out in order to prevent a Libyan campaign of terrorist attacks against United States nationals and targets, which there was good reason to believe was imminent, in the sense that the campaign was to be launched in the immediate future;
2. that no other effective means of preventing this terrorist campaign were available to the United States in the necessarily very short period before the terrorist attacks took place; and
3. that the air strike represented a use of force reasonably proportionate to the threat which it was designed to meet.Footnote 206
During the several years following the Tripoli attack, US legal analysts sought to further expand Greenwood’s broad reading of Article 51 to reach beyond State actors. Several suggested that if terrorists conducted a series of attacks and planned future ones, and their identities and whereabouts were known to the defending State, the conditions of lawful self-defence might be met, so long as the use of force was necessary and proportional.Footnote 207
In 1989 Judge Abraham Sofaer, Legal Adviser to the US State Department, argued that military force in self-defence targeting a single individual could be justified on the basis of Article 51 if that individual was suspected of terrorism. Sofaer went even further, arguing that the ‘inherent right of self-defence potentially applies against any illegal use of force, and that it extends to any group or State that can properly be regarded as responsible for [… terrorist] activities’.Footnote 208
The first major terrorist attack on the US planned from abroad and occurring after Sofaer’s argument was the 1993 truck bomb at New York City’s World Trade Center. Six people were killed in the blast and more than 1,000 were injured. The US employed law enforcement techniques to discover that the plot had been perpetrated by Al-Qaeda members. Six were arrested, successfully prosecuted, and sentenced to life in prison.Footnote 209
By 1998, however, the Clinton administration changed tactics. Al-Qaeda rigged more truck bombs and detonated them outside the US embassies in Nairobi and Dar-es-Salaam, killing and wounding hundreds, including twelve Americans. Clinton responded with air strikes on Sudan and Afghanistan.Footnote 210 The bombings had no detectable deterrent effect. In 2000, Al-Qaeda members attacked a US Navy ship docked in the port of Aden. Seventeen sailors died. The US again used law enforcement measures, working with Yemeni counterparts, to identify, detain and prosecute those who had carried out the attack, with considerable success.Footnote 211 Then, on 11 September 2001, Al-Qaeda members attacked again in the US, hijacking passenger planes and flying them into the World Trade Center, the Pentagon and a farm field. Within hours President George W. Bush declared a ‘war on terrorism’. On 7 October, the US, joined by the UK, attacked Afghanistan. Both States sent letters to the UN Security Council providing the Council with the required notice under Article 51.Footnote 212 The US letter cited the 9/11 attacks only and the Taliban government’s support for Al-Qaeda in Afghanistan:
In accordance with Article 51 of the Charter of the United Nations, I wish, on behalf of my Government, to report that the United States of America, together with other States, has initiated actions in the exercise of its inherent right of individual and collective self-defence following the armed attacks that were carried out against the United States on 11 September 2001 …
Since 11 September, my Government has obtained clear and compelling information that the Al-Qaeda organization, which is supported by the Taliban regime in Afghanistan, had a central role in the attacks. There is still much we do not know. Our inquiry is in its early stages. We may find that our self-defence requires further actions with respect to other organizations and other States. The attacks on 11 September 2001 and the ongoing threat to the United States and its nationals posed by the Al-Qaeda organization have been made possible by the decision of the Taliban regime to allow the parts of Afghanistan that it controls to be used by this organization as a base of operation.Footnote 213
The US did attack other States but did so covertly for the remainder of the Bush administration. No detailed legal memorandum was apparently prepared to justify military force against terrorists beyond Afghanistan, but the legal position can be deduced from public statements and conduct. The Los Angeles Times, for example, published a detailed account of a CIA drone attack in Yemen in November 2002 that left six men dead in a country not at war. The article stated that the US Air Force would not carry out the attack because of legal concerns.Footnote 214 The CIA continued to carry out such attacks in Pakistan and Somalia throughout Bush’s presidency.Footnote 215 The CIA also used a car bomb to assassinate a terrorism suspect in Syria in 2008.Footnote 216
Bush declared the United States to be involved in a ‘global war on terrorism’Footnote 217 and terrorists to be ‘enemy combatants’Footnote 218 who would be fought ‘until every terrorist group of global reach has been found, stopped and defeated’.Footnote 219 US National Security Adviser Condoleeza Rice explained the global war on terror was a ‘new kind of war’ to be fought on ‘different battlefields’.Footnote 220 Apparently, US officials believed being in a global war gave the legal right to target and kill Al-Qaeda suspects anywhere, including on the streets of Hamburg, Germany.Footnote 221
US Justice Department lawyers argued in Federal court that the US was in a worldwide war justified as self-defence.Footnote 222 Military operations were occurring far from Afghanistan. The November 2002 CIA attack in Yemen, mentioned above, targeted Abu Ali Al Harithi.Footnote 223 Harithi played no role in 9/11. He was killed in the attack along with a twenty-three-year-old American and four others.Footnote 224 In 2003, the US began military operations in Somalia.Footnote 225 In 2004, it began drone strikes in Pakistan.Footnote 226
When Barack Obama took office in 2009, he increased drone strikes. In March 2010, administration lawyers presented a modified version of the ‘global war on terror’ argument that began with 9/11.Footnote 227 The new claim blended both the ‘inherent right’ doctrine and the ‘terror attack/armed attack’ argument. The analysis rested on reading the Caroline incident as permitting attacks prior to an armed attack occurring. Obama’s lawyers moved beyond the Bush administration in re-defining ‘imminent’ to mean ‘not immediate’ and by arguing that crude bombs carried by a single individual are sufficient to count as an armed attack.Footnote 228
The legal advice cleared the way for the US to hunt for a reputed Al-Qaeda propagandist, Anwar al-Awlaki. After a failed attempt that killed two, Awlaki and several bystanders were killed in September 2011.Footnote 229 Less than two weeks later, the US attacked in Yemen again, killing Awlaki’s teenage son, also a US citizen, among others.Footnote 230
Greenwood, who had equated a series of terrorist attacks with the significant armed attack of Article 51, restricted his argument to State-sponsored terrorism. With 9/11, the US was following Sofaer’s extension to non-State actors. Greenwood objected:
In the language of international law there is no basis for speaking of a war on Al-Qaeda or any other terrorist group, for such a group cannot be a belligerent, it is merely a band of criminals, and to treat it as anything else risks distorting the law while giving that group a status which to some implies a degree of legitimacy.Footnote 231
Awlaki is not even known to have participated in a violent attack on a single American, let alone perpetrated anything like the sort of armed attack that could trigger self-defence under Article 51. He was a propagandist and lives on through his recorded sermons. He may now be more influential as a martyr than he was in life.Footnote 232
State-sponsored or not, terrorist attacks are rarely comparable to the type of attack envisioned in Article 51. Terrorist attacks require police work to gather evidence of responsibility. This can require days, weeks or even years to uncover sufficient evidence to foil future plots and bring suspects to justice. Article 51 sets the legal conditions to respond to an armed attack occurring when there is a need to defend. Terrorist attacks are usually brief and isolated. Swedish scholar Ingrid Detter writes, ‘International terrorism implies the intermittent use or threat of force against person(s) to obtain certain political objectives of international relevance from a third party. [T]he intermittent factor, which is a hallmark of terrorism, excludes it from constituting war per se.’Footnote 233 Responding weeks or months later becomes an unlawful reprisal, not an act of self-defence.Footnote 234
The armed attack/terrorist attack doctrine began with an attempt to replace the significant armed attack requirement of Article 51 with an accumulation of less significant, intermittent terrorist crimes. The doctrine was silent as to the duty of the defending State to target only a State bearing responsibility under principles of attribution. After 9/11, US administrations attempted to justify military force against States with no link of responsibility to attacks on the US. They then moved on to assert a right to use force against non-State actors with the potential and the propensity to use terrorism.
C. Unable/Unwilling
In 2006, Bethlehem joined an effort to draft ‘The Chatham House Principles of International Law on the Use of Force in Self-Defence’.Footnote 235 The document was sponsored by the foreign affairs think tank Chatham House (the Royal Institute of International Affairs).Footnote 236 One of the proposed principles, which Bethlehem has promoted since the publication of ‘The Chatham House Principles’, would allow States to attack non-State actors when those groups are located in another State that is ‘unable or unwilling’ to control them.Footnote 237
Presumably the point of this vague idea is that it frees the attacking State from the need to show a link of legal responsibility between the State being attacked and the non-State actors. Bethlehem may also consider the unable/unwilling idea to obviate the need for an invitation from a government to participate in a civil war. This second aspect of unable/unwilling is indicated by his expansion of what counts as consent in international law: ‘Consent may be strategic or operational, generic or ad hoc, express or implied.’Footnote 238 Where his flexible consent standards are not met, States could still exercise military force, under his unable/unwilling concept. Bethlehem’s proposal leaves it wholly to the State claiming a right of self-defence to determine what the terms ‘unable’ and ‘unwilling’ mean.Footnote 239
The terms are not used in the UN Charter, the drafts of the Charter, nor decisions of the ICJ on the use of force. Yet the UK Attorney General has used them and they appear in letters to the Security Council respecting the use of force in Syria by Australia, Canada, Turkey and the United States.Footnote 240 In a question to the US State Department Legal Adviser Brian Egan about the legal basis of ‘unable/unwilling’ by the author at a meeting of the American Society of International Law, he replied only that there are ‘some cases’ in support.Footnote 241 Shah believes Bethlehem developed the concept from Caroline.Footnote 242 The first use of the expression appears to have been in 1976 by the US representative to the UN when he spoke in support of Israel’s rescue operation at Entebbe, Uganda, saying, ‘[T]here is a well-established right to use limited force for the protection of one’s own nationals from an imminent threat of injury or death in a situation where the state in whose territory they are located either is unwilling or unable to protect them.’Footnote 243 Oscar Schachter believed the formula was drawn from Waldock’s Hague Lectures.Footnote 244 Waldock, drawing on Caroline, says something similar about rescue: ‘There must be (1) an imminent threat of injury to nationals, (2) a failure or inability on the part of the territorial sovereign to protect them and (3) measures of protection strictly confined to the object of protecting them against injury.’Footnote 245 Rescue of nationals is, of course, something quite different from the offensive use of force against non-State actors. ‘Failure or inability’ to rescue is a definite standard in the context of a hostage situation – either the victim has been liberated or not. Rescue could not contrast more starkly with the scenarios Bethlehem had in mind. The origin of ‘unable/unwilling’ in this very different context speaks against its use in regard to non-State actors.
Ashley Deeks, a long-time US State Department lawyer, has offered a different justification for ‘unable/unwilling’ – linking it to the venerable law of neutrality. She admits that ‘neutrality law does not directly govern uses of force between States and non-state actors’, but sees an analogy between States attacked by non-State actors and the territorial State where non-State actors are found and an ‘offended’ belligerent State vis-à-vis a neutral State.Footnote 246 The need for such an analogy seems unwarranted, however, given that international law has directly applicable rules and principles to govern State uses of force against non-State actors. Deeks discloses that her aim is to bolster the ‘unable/unwilling’ exception by linking it to existing law.Footnote 247
The article also supported the efforts of her former boss, US Legal Adviser to the State Department John Bellinger, to promote ‘unable/unwilling’ as customary international law.Footnote 248 Diplomatic cables obtained by Wikileaks describe steps to obtain expressions of opinio iuris from European governments that also involved Sir Daniel Bethlehem.Footnote 249 It is beyond the scope of this chapter to discuss whether such an effort, typical for treaty-making, can effect customary international law. Suffice it to say that the effort could not succeed in inserting ‘unable/unwilling’ into international law for several reasons. First, ‘unable/unwilling’ attempts to create a new exception to a peremptory norm, which cannot be done. Second, the attempt uses customary international law methodology to alter general principles of State responsibility and consent. Customary law methodology does not affect general principles. Finally, even if customary international law methodology did apply to these principles, the officials focused their confidential efforts mostly on Europe. They did not seek to establish a general State practice.Footnote 250 At the time of writing only five States have attempted to justify a use of force by invoking ‘unable/unwilling’ and those States have invoked other justifications in addition to ‘unable/unwilling’.Footnote 251 The case for opinio iuris is almost non-existent.Footnote 252
In 2016, for example, a joint committee of the British Parliament looking into the killing of Reyaad Khan provided this assessment of the international law on self-defence:
State practice since 9/11 certainly supports the view that a State’s right of self-defence includes the right to respond with force to an actual or imminent armed attack by a non-state actor, and the most recent UN Security Council Resolution 2249 (2015) lends support to this view. To be entitled to rely on self-defence against non-state actors, the State from whose territory the armed attack is being launched or prepared for must be unable or unwilling to prevent the attack.Footnote 253
The Parliamentary committee did not rely on ‘unable/unwilling’ alone. It also referred to Security Council Resolution 2249. That resolution, too, however, is insufficient to justify the UK’s attack in Syria. The Costa Rican scholar Nicolas Boeglin points out that the resolution falls well short of a Security Council authorisation for the use of force.Footnote 254 Without authorisation, the use of force in response to terrorism will be unlawful.Footnote 255 Boeglin believes France worked hard to convince its public that Resolution 2249 authorises the use of military force in Syria because it had no other possible justification. He further asks why France, the UK, the US and Australia have all made a considerable effort to expand the law of self-defence to permit force against non-State actors. He concludes that these efforts at expansion are a result of a pro-war mentality afflicting political leaders that biases them toward using military action, despite the poor results of armed conflict against non-State actors.Footnote 256 Boeglin rejects the view that violations of the Charter or of general principles of international law can yield new, permissive doctrines such as the unable/unwilling proposal.
None of the three doctrines reviewed here rest on persuasive arguments of legal change. US State Department Legal Advisor Egan said the US position rested on ‘cases’ without naming them. The UK Parliamentary Joint Committee asserted that State practice exists without listing any. Even the few examples of State practice that do exist are inconsistent. Much more is needed to anchor such highly indeterminate concepts as imminence, accumulation of events, inability and unwillingness. Even if the core features of the three doctrines were capable of incorporation in customary international law and sufficient State practice existed with an accompanying opinio iuris, customary rules may not derogate from a ius cogens norm. No one doubts this when it comes to norms such as the prohibition on genocide or slavery. Article 2(4) is also ius cogens and as such has a durability that contrary State practice, policy arguments, and even competing moral conceptions cannot undermine.
IV. The Prohibition on the Use of Force as Ius Cogens
Humanity has turned to law as an alternative to violence and status in ordering social affairs. Controls on the use of force and principles such as equality, necessity and proportionality are, therefore, essential to any legal system, going to the very reason for law. Such principles are found in the categories of general principles and ius cogens, and, given their essential role, require an explanation different from the vast majority of rules, principles and procedures. Most law is made through agreement – positive action – in the form of treaties, statutes or practice. It may be unmade using the same legal processes. Not so with these essential norms. They are discerned, rather than created through positive law method. Humanity has only one explanatory theory for law other than positivism, and that is natural law theory. It is natural law theory, therefore, that provides the explanation of ius cogens and general principles. Yet, the study of natural law has been in decline for a century. Scholars are turning to it once again,Footnote 257 but this section cannot draw on a well-developed current body of scholarship to support the analysis. The aim must be limited to offering evidence of the importance of natural law to ius cogens and the general principles and to invite further research.
The peremptory norms of international law are understood to be the prohibitions on the use of force, genocide, slavery, apartheid, widespread extrajudicial killing, torture and intentional targeting of civilians in armed conflict.Footnote 258 The list of inherent general principles is far longer. It includes principles associated with the proper administration of the law, such as equality, fairness and good faith, as well as principles associated with the operation of legal processes, such as necessity and proportionality. This section will discuss the meaning of ius cogens and inherent general principles and the implications for the law of self-defence that norms from these categories are seen as integral to the right of self-defence. Within the international legal community there is wide agreement that a category of norms exists known as ‘ius cogens’ and that these are norms superior to the positive law. The wide agreement on ius cogens extends to including the prohibition on the use of force. This section will offer additions to these points in the form of several logical corollaries. These corollaries include approaches to interpretation, the operation of customary international law and the emergence of new rules.
The first subsection below provides further description and evidence of the ius cogens prohibition on the use of force and the general principles of necessity and proportionality. Subsection B reveals the ancient origins of treating resort to war as a matter of grave moral and legal import owing to the conflict between violence and law. The final subsection will draw out the implications of the ius cogens character of the prohibition on the use of force, especially with regard to the accurate interpretation of rules and the understanding of legal change.
A. The Methodology of Ius Cogens
1. Characteristics and Evidence of Ius Cogens
Descriptions of the character of ius cogens as well as evidence of the existence of particular ius cogens norms can be gathered from the work of the UN International Law Commission (ILC), decisions of the ICJ and other courts, and the work of scholars. The best-known characteristic of ius cogens is found in the VCLT, drafted by the ILC. The VCLT makes clear that a treaty or treaty provision in conflict with ius cogens is void ab initio.Footnote 259 A treaty provision that conflicts with an emerging norm will become void.Footnote 260 This characteristic gives ius cogens a type of superiority to other principles and rules. The ius cogens norms form a barrier to action but do not compel action. To the extent that ius cogens norms are similar to rights, they are more like negative rights, such as the right to be free of torture. They do not establish positive obligations that might require the expenditure of resources. They do entail the affirmative duty of respect attaching to all legal prohibitions. Ius cogens norms work like principles of public policy or ordre public. In the law of contracts, a judge may apply public policy to void a contract, but she generally cannot prescribe obligations not indicated in the agreement of the parties. The same logic applies to ius cogens.
In 2012, in Jurisdictional Immunities of the State, the ICJ acknowledged the existence of the ius cogens category and indicated that the core civilian protections in time of armed conflict are ius cogens.Footnote 261 States are absolutely prohibited from violating these norms. That, however, is the extent of the ius cogens effect. States have no affirmative duty to craft remedies in national law for ius cogens violations. The fact that Germany violated ius cogens norms during World War II in intentionally targeting, enslaving and deporting civilians did not serve to negate Germany’s absolute sovereign immunity from national judicial process, which was the prevailing principle in the 1940s. Sovereign immunity is not, in itself, a violation of ius cogens. The applicants in the case tried to argue that ius cogens norms incorporate certain procedural rights to help secure remedies. The ICJ found this reasoning too attenuated. Every international legal principle is open to means of enforcement and remedies for violation. The doctrine of ius cogens does not require any specific remedy.
The ICJ has not discussed the source of ius cogens in any majority opinion. Contemporary scholarship appears divided between two views. One sees ius cogens as a form of ‘super customary international law’.Footnote 262 To be ‘super’, however, implies something other than regular customary international law. The other view holds that understanding the difference between a peremptory norm and a regular rule of custom requires drawing on natural law.Footnote 263
The most forthright evidence of ius cogens status for the prohibition on the use of force comes from the ILC. Drawing on the natural law tradition, the ILC developed the 1968 Vienna Convention on the Law of Treaties with two provisions, Articles 54 and 62, relating to ius cogens.Footnote 264 The commentary provides as an example of ius cogens ‘the law of the Charter concerning the prohibition of the use of force’. The ILC found that Article 2(4) ‘constitutes a conspicuous example of a rule in international law having the character of ius cogens’.Footnote 265 The ILC’s 2001 commentary to the Articles on State Responsibility also includes a supportive reference, but to the somewhat narrower prohibition of aggression: ‘It is generally agreed that the prohibition of aggression is to be regarded as peremptory.’Footnote 266
The ICJ has been more cautious than the ILC in how it has referred to ius cogens, but it did say in the 1986 Nicaragua case: ‘Article 2, paragraph 4, of the Charter of the United Nations … is frequently referred to in statements by State representatives as being not only a principle of customary international law but also a fundamental or cardinal principle of such law.’ The Court proceeded to cite the ILC’s comment that Article 2(4) is a ‘conspicuous example of a rule in international law having the character of ius cogens’.Footnote 267
ICJ judges have been more expansive in their individual opinions in stating that the prohibition is ius cogens. For example, Judge Elaraby expressed his view in The Wall that ‘[t]he prohibition of the use of force … is universally recognised as a ius cogens principle, a peremptory norm from which no derogation is permitted.’Footnote 268 In 1970, the ICJ made an indirect reference to ius cogens norms in its decision in the Barcelona Traction case. In listing erga omnes obligations, it included the international law ‘outlawing of acts of aggression, and of genocide’ as well as ‘the principles and rules concerning the basic rights of the human person, including protection from slavery and racial discrimination’.Footnote 269
Relying on the American Law Institute’s Restatement (Third) of Foreign Relations Law, a US Federal court judge cited the prohibition on the use of force as ius cogens in a case brought by plaintiffs attempting to enforce US compliance with the Nicaragua judgment. ‘The … Restatement acknowledges two categories of [ius cogens] norms: “the principles of the United Nations Charter prohibiting the use of force”, … and fundamental human rights law that prohibits genocide, slavery, murder, torture, prolonged arbitrary detention, and racial discrimination …’Footnote 270 Louis Henkin was the chief reporter of the Restatement. He argued in other writing that the prohibition ‘is the principal norm of international law of this century’.Footnote 271 Orakhelashvili represents the consensus scholarly view in saying: ‘The prohibition of the use of force by States undoubtedly forms part of ius cogens.’Footnote 272
Despite this evidence, some authors have questioned whether Article 2(4) can be ius cogens if it has exceptions.Footnote 273 Their view, however, confuses the substance of the norm with a derogation from it. Self-defence is part of what constitutes the prohibition on the use of force. It is not a derogation from the prohibition. Orakhelashvili has replied to this confusion by saying the whole of the ius ad bellum is ius cogens.Footnote 274 He is also not entirely correct, however, because necessity and proportionality are part of the ius ad bellum but are general principles of law, not ius cogens. General principles are also non-derogable but lack the substantive moral content of peremptory norms, as will be discussed next.
2. General Principles of Necessity, Proportionality and State Responsibility
Certain general principles have similar characteristics to ius cogens but are more procedural than ethical in nature. The general principles of necessity, proportionality and attribution are general principles and essential components of the lawful resort to force. These principles are discerned much as peremptory norms are, through natural law method, discussed in more detail in section IV below. General principles inherent to the law are distinguishable from the general principles found by searching national legal systems to find a common rule, which tend to be based on national legislation, a consent-based or positivist source.
As mentioned above, the ICJ classified necessity and proportionality as rules of customary international law in the Nuclear Weapons case.Footnote 275 The Court provided no basis for this categorisation. It cited no State practice or opinio iuris. Nor are these the type of principles that could be eliminated from the law. For these reasons, they fit the category of general principles better than customary international law. Both Judith Gardam and Bin Cheng take the position that necessity and proportionality are general principles.Footnote 276 Like peremptory norms, inherent general principles are formed through means other than voluntary consent or other affirmative material acts. Peremptory norms are distinguishable in that general principles tend to condition processes, while ius cogens norms have ethical or moral content. The process of using force, for example, is regulated by necessity and proportionality.
When necessity and proportionality are correctly categorised as general principles, rather than rules of customary international law, it is possible to accurately assess their role in regulating the use of force. Necessity limits the use of force to a ‘last resort after all peaceful means have failed’.Footnote 277 In addition, the principle requires that the party resorting to force must calculate that there is a high likelihood of success that force will accomplish the legitimate objective.Footnote 278 In this sense, Brownlie has called the principle of necessity ‘innate in any genuine concept of self-defence’.Footnote 279
Proportionality is equally innate. Force used in self-defence must not be excessive in relation to the injury. The ICJ has mentioned necessity and proportionality as conditions of the lawful resort to force in a number of its decisions. In the Nicaragua case, the Court said that even if the evidence proved a significant armed attack attributable to Nicaragua, the US response had to be necessary and proportionate.Footnote 280 In the Oil Platforms case, the US failed to prove that Iran was responsible for attacks on US ships. Even if it had proved Iran was responsible, the Court indicated that the US response was disproportionate.Footnote 281
The US adhered more closely to the requirements of necessity in leading the coalition that liberated Kuwait from Iraq in 1991. In August 1990, Iraq invaded Kuwait, quickly overwhelming Kuwait’s small military. The UN Security Council became involved and, after a period of attempting to use economic sanctions to persuade Iraq to withdraw, the Council authorised a coalition of States to use force to liberate Kuwait. The coalition forces quickly drove Iraq’s armed forces out of the country and drove them beyond a swathe of territory that later became a demilitarised zone for Kuwait’s security. Famously, the coalition did not proceed to Baghdad to remove Saddam Hussein from power, because doing so, in the view of coalition leaders, was not necessary to the liberation of Kuwait. Indeed, fighting unrelated to the liberation of Kuwait could not be justified under the principle of necessity, since it was clearly beyond the force required to remove the occupier. Failing to respect the principle of necessity would make any killing and destruction both unnecessary and disproportionate.Footnote 282
In Afghanistan, after the Taliban fled the capital, Kabul, in December 2001, any further use of force was arguably unnecessary to accomplish self-defence.Footnote 283 By mid-2002, with Hamid Karzai’s elevation to the leadership of Afghanistan, international forces shifted the purpose of fighting to supporting his government. The armed conflict in self-defence became a counter-insurgency or civil war.
US and UK drone operations since 2001 also raise the issue of compliance with the principles of necessity and proportionality. Scholars have debated the possible violations of the ius ad bellum, ius in bello and human rights norms involved in such operations that aim at killing individuals on a ‘kill list’ and are now referred to as ‘targeted killing’ operations.Footnote 284 Necessity and proportionality are rarely mentioned in the legal analyses. After a decade and a half of these operations, Al-Qaeda continues, and more virulent offshoots, such as ISIS and Boko Haram, have emerged. If the self-defence aim of targeted killing is to suppress these non-State actors, the record is one of consistent failure. The United Kingdom certainly had a heavy burden to meet in demonstrating that killing Khan in 2015 was necessary and proportionate. The US had the same burden in the killing of Hussain.
Both States fell far short of meeting that burden. References were made only to the victims’ past actions. The Guardian newspaper reported that in the announcement of the killings ‘Cameron referred to Khan and Hussain planning an attack, but in its briefing to reporters later, Downing Street referred to events that had happened long before they were killed.’Footnote 285 The drone strike was not a response to violence happening at that moment. Thus, the attacks on Khan, Hussain and others have the character of unlawful reprisal attacks, not action in self-defence.Footnote 286 The right of self-defence is a right to use force to repel an attack in progress,Footnote 287 to prevent the near-time attacks that will occur as part of the attack in progress, or to reverse the consequences of an attack, such as ending an occupation. In these situations, necessity and proportionality can be calculated.
The 2011 intervention in Libya by NATO members and others further demonstrates the importance of compliance with necessity and proportionality. In March 2011, the Security Council authorised States to use military force to protect civilians in the Libyan civil war.Footnote 288 Virtually no attempt at negotiation was made and no alternatives to force were tried, such as protected corridors for refugees to move to safe areas. It seemed clear soon after NATO began attacks in Libya that the alliance’s military objective was to oust Ghaddafi, not simply civilian protection.Footnote 289 Russia and China argued that fighting to change the regime exceeded the Security Council’s mandate and was thus a resort to unlawful force.Footnote 290 As many as 30,000 people died – many, if not most, civilians – in about six months. With the fall of Ghaddafi, near anarchy erupted and more civilians died. If the principle of necessity had been taken seriously, such widespread fighting would not have been initiated, even if the Security Council had authorised it. As a general principle, all uses of force must meet its requirements, whether in self-defence or with Security Council authorisation.Footnote 291
South Korea has modelled compliance with necessity and proportionality. North Korea has attacked it with missiles and other forms of force many times since the end of the Korean War. Despite this, South Korean leaders have exercised restraint in launching counter-attacks, calculating they will have little positive effect. This was the case even prior to North Korea acquiring a nuclear weapon.Footnote 292
B. History, Morality, Natural Law
The ancient prohibition on the use of force with its narrow allowance for self-defence in situations of necessity is found in the earliest discussions of law between communities. Prior to the European Enlightenment and the rise of positivism, legal theory explained the content of law as incorporating mostly positive law but within a frame of principles ordained by divine command. The ius ad bellum was one of the last areas that continued to be explained through natural law.Footnote 293 Then, just as the international legal community lost nearly all knowledge of natural law, scholars began again to argue that ius cogens principles as well as legal authority in general require more than positivism. The discussion below describes both the ancient origins of the prohibition on the use of force as a moral and legal precept and the reappearance of natural law along with the new interest in ius cogens.
Historians consistently find the earliest direct antecedents of today’s prohibition on the use of force in the Christian Just War Doctrine that emerged in the fifth century and drew on Roman, Greek and Jewish teaching in addition to Christianity.Footnote 294 Proponents of the Just War Doctrine sought to end the early Church’s ‘extreme pacifism’.Footnote 295 As Christianity became ‘linked with the secular power of the Empire’, Saint Augustine of Hippo presented theologically based arguments for allowing limited resort to force in self-defence, as well as to restore stolen property, to deter future wrongs and to promote Christianity.Footnote 296 Some later Christian groups, including Quakers, Mennonites and the Amish, returned to a commitment to total non-violence, but most have followed Augustine. Over the centuries, a complete reversal has occurred in some quarters. From a narrow exception for situations of extremes, certain Just War theorists extol the virtue of war in good causes.Footnote 297
Saint Thomas Aquinas systematised Just War teaching in the thirteenth century into a set of law-like principles that required a declaration by a right authority, a just cause, the right intention on the part of the authority, and compliance with the principles of necessity and proportionality.Footnote 298 Self-defence was among the just causes. Aquinas used natural law method in developing his Just War principles. For him this method combined the use of reason – informed by education, experience, and divine revelation – and reflection on humanity’s social nature and the observable order of the natural world.Footnote 299
Aquinas fused reason, openness to transcendence, and observation of nature as sources of guidance and authority. This three-part, interconnected synthesis for natural law method had evolved over centuries.Footnote 300 Aquinas understood legitimate positive law to be consistent with norms derived from natural law method and thereby with the good.Footnote 301 He explained that the vast majority of law is derived from positive sources – legislation and practice – but that it exists within a frame of natural law. The application of natural law method results in more complete explanations than are available in positive law theory, answering such questions as to why law has authority in society and what principles are essential and, therefore, unalterable through positive law method, including the restrictions on resort to war.Footnote 302
Figures such as Hugo Grotius sought to retain natural law method without the intermediation of Catholic Church clergy. He argued, in distinction to other Protestants, such as Alberico Gentili, for a limit on individualistic determinations of ultimate morality. With respect to the Just War Doctrine, for example, Grotius argued for retaining the brief list of just causes used since Augustine as the chief means of restraining resort to war.Footnote 303 Grotius’s seminal work, On the Law of War and Peace (1625) aimed at the Thirty Years’ War and mitigating its barbarism. Grotius wanted to inspire greater humanity in the conduct of the war and encourage the establishment of a legal order superior to the warring factions after the war. A group of legally co-equal sovereign States did in fact emerge in Western Europe under the treaties known as the Peace of Westphalia (1648). Grotius’s comprehensive treatise provided the legal blueprint for the new world order. In the prologue he made the decisive point that both allowed Europeans to move past their religious differences to agree to peace, but also contributed significantly to the undermining of natural law theory and the Just War Doctrine based upon it. To win the adherence of both Protestants and Catholics to one unified law, Grotius famously wrote:
What we have been saying [about law] would have a degree of validity even if we should concede that which cannot be conceded without the utmost wickedness, that there is no God, or that the affairs of men are of no concern to him.Footnote 304
It was this concept that began the process of eliminating reference to a divine basis of legal authority in the West. Grotius’s proposition helped avoid theological disputes in winning adherents to international law, doing little immediate harm as the Western conception of law continued to benefit from the centuries of association with belief in divine authority.
Each decade after Grotius, however, the assumed tradition supplying the frame of international law within which the positive law exists has thinned.Footnote 305 Some theorists view the move away from religion to be a move to greater sophistication and rationality.Footnote 306 Removing particular religious understandings of transcendence from natural law was a rational response to the new, more pluralist understanding of contemporary society.Footnote 307 However, without an alternative explanation as to why some legal principles are superior to positive law rules, misunderstanding was bound to arise. After Grotius, scholarship on the normativity of international law increasingly narrowed towards exclusively positivist theories. The Swiss jurist Emer de Vattel did great damage to the theory of law as superior to political communities or sovereigns by returning to the argument that the sovereign alone may judge the lawfulness of her own actions.Footnote 308 After Vattel, the concept grew steadily that law is what the sovereign wills, and international law could, therefore, be no more than the consensus of State will, unrelated to any higher source.
With the rise of positivism and sovereign absolutism, the reasons for adherence to the Just War Doctrine became increasingly unpersuasive. Nevertheless, the Doctrine did not disappear. European powers developed various justifications for waging wars to take and control colonies. Inconsistencies between actual practice and the Just War Doctrine grew, but States did, in fact, continue to proclaim the justice of their causes.Footnote 309 States attempted to avoid the implications of formally declaring war by engaging in force short of war or reprisals.Footnote 310 They presented arguments as to why the use of force met the requirements of necessity and proportionality.Footnote 311
Proof of the continuing vitality of the Just War Doctrine through the nineteenth century is provided by the same correspondence over the 1837 Caroline incident Bowett used to attempt to weaken the restrictions on the use of force. The correspondence between Webster and Ashburton was over the meaning of the law restricting resort to force outside of any treaty.Footnote 312
Natural law teaching on war was also retained through transformation into positive law. The Paris Declaration on Maritime Law of 1856 had provisions regulating the conduct of maritime warfare, including outlawing privateering.Footnote 313 In 1899, States adopted the First Hague Peace Convention, which required States to seek alternatives to resort to force. In 1907, at the Second Hague Peace Conference, more conventions were adopted to prevent and mitigate armed conflict. The First Hague Peace Convention of 1907 on peaceful settlement of disputes expressed the purpose in Article 1 to be ‘obviating as far as possible recourse to force in the relations between States’ and ‘to ensure the pacific settlement of international differences’.Footnote 314 These developments in positive law further occluded the gap in legal theory left through suppression of natural law.
Into the early twentieth century international law scholars continued to acknowledge a role for natural law, especially regarding resort to force. One of the most prominent international law scholars of the time, Lassa Oppenheim, felt the need to continue arguing against natural law and its proponents, who seemed to him to disagree about the most basic issues.Footnote 315 The 1906 edition of his influential treatise refers to peace activists as ‘fanatics’.Footnote 316 Oppenheim’s protests are just another indication, however, that in fact governments and scholars persisted in looking to the natural law doctrine of Just War. Those who saw it as their mission to rid the world of any vestige of natural law never in fact succeeded.Footnote 317
By the end of the First World War it was quite clear to some legal scholars that the theory of absolute sovereignty had gone too far. They were blaming the ‘crude’ positivism of the previous century for the understanding that no law existed above positive law made by States.Footnote 318 Positivism contained no explanation to use against the dictators emerging in Europe with aggressive designs on other States. Those designs were, after all, an exercise of State will. If a positive law obstacle stood in the way, such as The Hague Conventions, a State need only withdraw its consent to be free to act.Footnote 319
Others, however, returned to natural law to revive some restraining principles superior to the will of States. Hans Kelsen, a critic of natural law, nevertheless incorporated key natural law concepts in his view of war and his theory of legal authority. Kelsen understood the sanction to be an integral part of any legal rule. For Kelsen, war and reprisals, subject to constraints, were the necessary legal sanctions of international law.Footnote 320 Kelsen responded to those who believed all war to be unlawful by saying that the only way to respond to unlawful war was with war. Logically all war could not, therefore, be considered unlawful.Footnote 321 War in the classic thinking of the Just War Doctrine could be lawful. Kelsen found positive evidence that the Just War Doctrine persisted in international law in provisions of the Treaty of Versailles, the Covenant of the League of Nations and the Kellogg–Briand Pact.Footnote 322 Kelsen interpreted all of these agreements as permitting the use of force to respond to unlawful war.
At the same time, the Just War Doctrine did not permit unfettered war. Kelsen credited Augustine, Aquinas and Grotius as developing the idea of war being forbidden except in a just cause.Footnote 323 The increasing rejection of the Just War Doctrine during the nineteenth century came in connection with the emergence of theories promoting absolute State sovereignty.Footnote 324 Those theories challenged all international law, not just the limitation on war. They had to be rejected, and, in doing so, the main objection to restricting war disappeared too.Footnote 325 Kelsen was alert to the quixotic position of scholars like Oppenheim who took the view that while war could not be restricted, measures short of war or reprisals could be regulated.Footnote 326 After the Second World War, Kelsen described the UN Charter prohibition on the use of force as an instantiation of the Just War Doctrine.Footnote 327
The catastrophe of World War II drew some others back to natural law. For German scholars Theodor Adorno and Gustav Radbruch, positivism, shorn of any connection to natural law, had played a significant role in persuading large populations of the legality of Fascist policies.Footnote 328 Adolf Hitler was elected ostensibly in compliance with the German constitution and was, therefore, the legitimate leader who could command obedience. The courts enforced the laws adopted by parliament. After the War, in the famous trial of the judges, a standard defence was that a judge’s job is to enforce the law developed following legally instituted procedures. Judging morality is not the job of a positive law court.Footnote 329 Prosecuting German and Japanese leaders required confronting this defence. According to David Luban and co-authors, Article 8 of the Nuremberg Charter relies on natural law in restricting the defence of acting ‘pursuant to an order of his government or a superior’.Footnote 330 Thus, natural law ‘form[s] the most obvious justification for criminalizing “murder, extermination, enslavement, deportation, and other inhumane acts” … whether or not in violation of domestic law’.Footnote 331 The influence of natural law can also be seen in the Nuremberg Tribunal’s characterisation of aggression as the ‘supreme international crime’.Footnote 332
In 1946, Sir Hersch Lauterpacht also re-presented law as a hybrid system of positive and natural law.Footnote 333 Lauterpacht understood that all law consists of both forms, but argued that while this fact could be merely assumed for national legal systems, it had to be openly acknowledged in the case of international law. International law has a unique role in regulating relations in a system of diverse nations and cultures lacking regular governmental institutions of courts, legislature and executive. At the international level, ‘the function of natural law, whatever may be its form, must approximate more closely to that of a direct source of law.’Footnote 334 Lauterpacht did not provide an explanation of what exactly natural law is, or how it can approximate a direct source of law. He did point to certain ‘features’ of natural law that he considered essential to international law, including the comprehension of law as superior to ‘the totality of international relations’. He credited Grotius with endowing international law with ‘unprecedented dignity and authority by making it part not only of a general system of jurisprudence but also of a universal moral code’.Footnote 335
ICJ Judge Kōtarō Tanaka also made a case for natural law in his dissenting opinion in the 1966 South West Africa cases.Footnote 336 Other international law theorists, such as Verdross, worked to revive natural law, providing the reasoning for acceptance today that the Charter prohibition on force and principles related to it respecting the right to life and civilian protections in armed conflict are ius cogens, peremptory norms. Writing recently, ICJ Judge Antônio Augusto Cançado Trindade and former judge Christopher Weeramantry also support renewed understanding of natural law.Footnote 337 The important point for this discussion is that the peremptory norms and inherent general principles have a distinctive theoretical basis in international law. The ancient history of restraint on resort to force reflects deeply held moral precepts, moral precepts further reflected in the natural law method developed to account for non-derogable legal principles and the basis of legal authority. Using the approach of natural law, judges, delegates to a negotiating conference, or other representatives of the community with authority to participate in legal process continue to reflect the approach associated with Aquinas of discerning ius cogens by employing reason and reflecting on human nature and the natural world, while remaining open to transcendence.Footnote 338 Aquinas looked to revelation for understanding transcendence. Philosophers in our secular age see secular paths leading to the same concepts, especially in aesthetic philosophy, the study of beauty.Footnote 339
C. The Implications of Ius Cogens Status for Self-Defence
Certain conclusions flow from the status of the prohibition on the use of force as a peremptory norm. One critical conclusion is that under international law, no other norms or values are superior. The other ius cogens norms are co-equal; all other norms and values are inferior. Inferior norms do not trump superior norms. Another conclusion is that peremptory norms require a conservative approach to interpretation of the norm itself and related provisions, such as Article 51 of the UN Charter. Indeed, the drafters of the Vienna Convention understood that interpreting ius cogens might require the intervention of the International Court of Justice and provided for that possibility in Article 66. These prohibitions are durable and impervious to diminution. Interpretation that permits conduct contrary to the established meaning of the norm is a form of derogation. State practice contrary to the prohibition cannot modify it; contrary practice is a violation of the prohibition.
Finally, peremptory norms are not ‘frozen’. They may expand, reaching more conduct, such as the use of force to wage civil war. Again, the Vienna Convention points to the possibility of expansion in Article 64, which refers to the ‘emergence’ of new ius cogens. Expansion of peremptory norms is not impermissible derogation. It is consistent with the ethos of ius cogens.
1. Peace as the Superior Moral and Legal Norm
Proponents of force against non-State actors, for humanitarian purposes, arms control, and other goals, often use arguments from morality to justify violating the prohibition on the use of force. The arguments parallel the standard civil disobedience reasoning that the moral rightness of using force excuses the legal violation. This line of thought seems to overlook that the prohibition on force is not a mere positive rule that is less important in the moral universe than the advocate’s own normative goal. Peremptory norms prohibit conduct; they do not command it. No logical reason exists to violate one peremptory norm to advance another. No State could excuse the use of torture to advance the prohibition of genocide. The same is true of the prohibition on the use of force. In the case of a value such as national security, the argument is even stronger. The prohibition on the use of force is ius cogens and may not be violated to advance national security. Other ways must be found consistent with the norm.
In the issue area of use of force against non-State actors, the value being juxtaposed to the prohibition on force is typically security. The sort of argument has become familiar, owing to advocacy for humanitarian intervention. Supporters of humanitarian intervention tend to accept that they stand on weak legal grounds and seek to substitute moral arguments as supplementary legal ones. The great suffering of victims is used to argue for a lower quantity of evidence to support reinterpretation, modification or addition to the Charter exceptions for resort to force.Footnote 340 Without the moral argument, the legal argument would likely be dismissed out of hand. Another approach accepts that the legal basis for humanitarian intervention is weak but finds sufficient support to place humanitarian intervention in a ‘grey area’ of illegality.Footnote 341
In the pursuit of security against non-State actors, Orna Ben-Naftali says States have developed a ‘theology of security’.Footnote 342 This theology involves believing that an increase in one’s own sense of security is acceptable even at the cost of limiting the right to life of another, generally a person outside one’s community. This notion places security as a value ahead of the peremptory norm prohibiting force. Advocates for expanding the legal right to resort to force tend to ignore this basic legal fact. They also tend to begin analysis with the exception to the prohibition in Article 51, rather than the prohibition, and from Article 51 their argument continues with policy reasons why governments should have a wide-open right to resort to military force against enemies, whether the Irish Republican Army, Hezbollah, the PKK, Abu Sayyaf, the FARC, Al-Qaeda, Al-Shabab, Boko Haram, ISIS, or others. The reason these groups are or have been the enemy is because they use violence and violate the right to life and other human rights in promoting their causes. The law against force is in favour of the right to life and forms the very foundation of orderly life in society.
As discussed above, the doctrine of ius cogens rejects the argument that violating a peremptory norm is justifiable to promote another ius cogens or other important norm.Footnote 343 Even if the prohibition on force were not ius cogens, arguments based on national security, necessity, or even the protection of the right to life would still fail. Inherent in such attempted justifications is the contradiction that it is acceptable to kill and injure some, even wholly innocent people, to preserve the human rights of others.Footnote 344 Ian Brownlie raised concerns about believing in the use of military force to accomplish the protection of human rights in the 1970s.
[T]hose making novel proposals need to produce more evidence. What is the price in human terms of intervention? What were the casualty ratios in the Stanleyville [Congo] operation in 1964, the Dominican Republic in 1965, and other possible examples? How many were killed in order to ‘save lives’? To what extent does the typical intervention cause collateral harms by exacerbating a civil war, introducing indiscriminate use of air power in support operations, and so on?Footnote 345
International law has other ways to counter terrorism and advance human rights, including the right to life, without violating the prohibition on the use of force. Proposing the expansion of the right to use force to these new causes reverses the assumption upon which the right to resort to force is tolerated in international law. Under the Charter, military force in self-defence is lawful to counter unlawful military force by or attributable to a State with a government and territory. The Charter does not expressly reach civil war, but international law principles in that context, too, are designed to apply to a contention among armed groups using military force to control territory.Footnote 346 The law of self-defence does not envision using military force to try to affect the kind of social change needed to supress terrorist crime or deter human rights violations. Whether or not the Security Council has the legal right to authorise such use of force is beyond the scope of this chapter. Suffice it to say here that the history and structure of law restricting the use of force supports the conclusion that violating the prohibition on the use of force is immoral and impractical regardless of the aim. The law supports seeking alternatives to military force under the justification of self-defence.
In any case of uncertainty, situations where a ‘blurring of the lines between war … and countering the crime of terrorism’Footnote 347 takes place, the logic of ius cogens requires adherence to peacetime law. The whole body of international law is structured to move toward eliminating war. The exceptions to the prohibition of force and in IHL are designed to apply in narrowly defined emergencies. The argument that it is too difficult to comply with the restrictions on the use of force is misleading. Nothing is easier than not killing. Pacifists are willing to be killed by an attacker rather than risk killing in an act of self-defence. The idea that not killing is hard has grown out of the false assumption that military force is an effective tool against terrorism and in support of human rights. Foreign policy realists, weapons manufacturers and even some academics advance this myth despite the substantial social science evidence to the contrary.Footnote 348
2. Peremptory Interpretation/Irrelevant State Practice
Little has been written on the proper approach to interpreting ius cogens. Expansionists attempt to use State practice to show that the Charter provisions have changed and are weaker, posing less of a barrier to State use of force.Footnote 349 Indeed, much of the standard work on self-defence looks to State practice, such as the use of force against non-State actors beyond armed conflict zones or the use of force without a territorial State’s express consent, to argue that these law violations are capable of diluting the restrictions in Article 51.Footnote 350 Given the nature of peremptory prohibitions, however, valid interpretation must not result in a weaker norm. Logically, peremptory norms may expand, not contract.
As a theoretical matter, attempting to create a new treaty rule or a rule of customary law that derogates from a ius cogens prohibition may be distinctive from derogation through interpretation. As a practical matter, the two processes are indistinguishable. Indeed, it is sometimes difficult to tell whether an expansionist is invoking State practice as evidence of a new rule of customary international law or as subsequent practice relevant to rule interpretation.Footnote 351 When peremptory norms are newly discerned, the discovery may lead to invalidating existing treaties and rules of custom.Footnote 352 Similarly, interpretation can lead to greater restrictions where aggression, genocide, torture, or another peremptory prohibition is concerned, not lesser. In any case of doubt as to a prohibition’s reach, the presumption favours treating more conduct as restricted, not less.Footnote 353 This means, for example, that reading Article 51 as permitting self-defence before an armed attack occurs, as the inherent right doctrine permits, would be an incorrect reading, given the nature of the prohibition. The same may be said of removing the significance requirement respecting the armed attack and the attribution requirement for the target of military action in self-defence.
If Article 2(4) were just a treaty principle or rule of customary international law, standard interpretation rules would include subsequent practice as a guide to meaning, even to some extent meaning that changes over time.Footnote 354 As ius cogens, however, meaning is stable, and contrary State practice is of little relevance. States acknowledge that the prohibition on the use of force is ius cogens but overlook this point about interpretation and the impact of State practice. To avoid diluting Article 2(4), Article 51 must be interpreted to limit weakening the general prohibition. Only State practice indicating discernment toward a rule with wider reach is consistent with the ‘no derogation’.
The general principles of necessity and proportionality that are part of the prohibition on the use of force must also be interpreted conservatively, as must the principles of State responsibility. State responsibility principles of attribution as well as consent require clear and convincing evidence provided openly for the members of the international community to assess.Footnote 355 Consent as a defence in the law of State responsibility is ‘subject to the limitation codified in Article 26 of the Articles on State Responsibility (ASR): they may not be invoked against peremptory rules’.Footnote 356 The unable/unwilling doctrine substitutes the attacking State’s subjective assessment that another State is not managing a problem of terrorism for the target State’s consent. The better position in light of the peremptory status of the prohibition is that only express and public consent is adequate to permit the lawful use of force on another State’s territory. The Nicaragua case supports this position on consent.
Even if new interpretations could result in weakening the prohibition on the use of force, the current arguments aiming to do so tend to be insufficient to create valid, new interpretations, even of standard treaty and customary rules. The arguments are consistently a form of special pleading, intended for particular States and not the international community as a whole. Bowett states expressly that he had the Suez Crisis in mind in developing the ‘inherent right’ doctrine. Greenwood’s approach to regard terrorist attacks as armed attacks was a defence of the US attack on Libya. Bethlehem focused in 2012 on American uses of military force in the terrorism context. Each was written after a use of force and each supplied a novel argument of post hoc justification.
These novel approaches to the law of self-defence seem to be designed for a few select States only.Footnote 357 The US and UK may resort to force when they deem another State ‘unwilling’ or ‘unable’ to respond adequately to terrorism but not others. The United Kingdom may use a drone-launched Hellfire missile to kill a person and bystanders in Syria to prevent a potential future terrorist attack at home, but China may not use the same weapon and rationale to kill an organised crime figure in Myanmar. The US claims a right to carry out drone strikes in Yemen against a man implicated in violent, anti-US propaganda because Yemen is unable or unwilling to control the suspect, but Russia cannot claim the same right to kill individuals considered a danger to the stability of its government living in the United Kingdom. This exceptionalism is an assumption of some government officials. An adviser to the former UK prime minister Tony Blair made the point as plainly as possible: ‘The challenge … is to get used to the idea of double standards. Among ourselves, we operate on the basis of laws … But when dealing with more old-fashioned kinds of states … we need to revert to the rougher methods of an earlier era – force, pre-emptive attack, deception.’Footnote 358
A subtler approach relies on an idea related to customary international law formation that some States are ‘specially affected’ and that their practice and opinio iuris should have greater weight.Footnote 359 This idea has been used to assert that ‘legal advisers from the defence, intelligence, and security services of reputable governments, should be accorded more weight because of these states’ experiences countering new threats with new technologies that only these states possess.’Footnote 360 The rules that emerge advantage these States.
There is, however, no ‘among ourselves’ or States with greater weight when it comes to international law. States are equal before the law. Neither democracies, States with major military forces, nor any other has greater rights to resort to force. As Dire Tladi discusses in his chapter, the International Law Commission rejected a proposal to favour the ‘specially affected’ State in customary law formation.Footnote 361 Even if such a status existed, no State can claim to have exceptional rights based on being the victim of terrorism or in possession of high tech weapons like drones. The problem of terrorism is too widespread, and States do not retain monopolies on weapons technology. These arguments, once made with a Prime Minister Cameron or President Obama in mind, may appear quite differently to advocates when contemplating their use by a President Trump. Additionally, the poor results of using force in violation of the law continue to mount. It is a record of human tragedy that should undercut exceptionalist stances.Footnote 362
3. Progressive Development Toward Peace
While diluting and contracting the prohibition on the use of force through interpretation is impermissible, discerning a broader prohibition is not. Interpreting the meaning of peremptory norms logically follows the principle of progression: the prohibitions on aggression, genocide, torture, and other egregious conduct may expand to reach more conduct in the future, not less.Footnote 363 This means that stretching analogies to allow more force is an invalid approach. The analogies between armed conflict and intermittent terrorist attacks or consent and implicit acquiescence because a State is ‘unable or unwilling’ to control terrorism are invalid.
One obvious area to expand the prohibition on the use of force is to reach civil war. The natural progression of the prohibition is to obligate non-State actors not to engage in military force. Non-State actors are already obligated not to kill under national criminal and international human rights law. Some may believe that once individuals form a group and struggle to secede or throw off an oppressive government, they are no longer bound by the national criminal law or the protection for the right to life. While it is true that, if such a group engages in fighting that has reached the level of armed conflict, aspects of IHL apply, no one has the right to initiate internal armed conflict by killing government forces or using excessive force against rebels. This principle could be incorporated into the ius ad bellum, raising the visibility and status of the prohibition on initiating military force. With greater awareness of the prohibition, non-State actors might be persuaded to adopt non-violent approaches.
Including initiation of civil war in the prohibition would also result in a limit on the right to assist governments fighting non-State actors within their own borders. The prohibition on the use of force in Article 2(4) by its plain terms prohibits assisting a government in fighting rebels. Presumably, any such use of force would require Security Council authorisation to be lawful. Nevertheless, governments have regularly intervened in internal conflicts in colonies and where a puppet government has been installed for the very purpose of making the invitation. The practice should end for all the normative reasons already discussed but also because the record of intervention on the side of governments is one of consistent failure. Consider the many interventions by France in former colonies – more than twenty within a period of forty years.Footnote 364 The intervention in the Central African Republic that began in 2013 has not only done little to improve stability, French troops were implicated in child sex abuse.Footnote 365 The record of intervention on the side of governments is one of extending conflict and keeping authoritarian, unpopular leaders in power.
This section has highlighted three significant implications that follow from the ius cogens status of the prohibition on the use of force. First, peremptory norms embody the international community’s highest normative principles. Claims for the right to use military force outside the established limits of the prohibition by claiming a morally superior purpose must fail as a legal matter. Under international law, ius cogens norms are co-equal. One may not be violated in the pursuit of another, if that is even possible. Inferior norms do not trump superior ones.
The second implication is that peremptory norms require a conservative approach to interpretation. Contrary State practice does not open the way to new, more relaxed understandings of the prohibition. In terms of the three pernicious doctrines, the words ‘if an armed attack occurs’ cannot be read out of Article 51. Low-level, intermittent terrorist attacks do not satisfy the significant armed attack requirement, nor may the ‘unable/unwilling’ doctrine substitute for attribution or consent.
Finally, peremptory norms may be discerned to reach more conduct, not less. Expansion of peremptory norms is consistent with the ethos of ius cogens, expansion, for example, to prohibit the initiation of civil war under the ius ad bellum.
V. Conclusion
The purpose of law is peace. Law emerged in communities as an alternative to physical force, religion, and status for the settlement of disputes on the basis of the principle of fairness – of treating like cases alike. Sophisticated law builds on this foundation to foster not just negative peace – the absence of violence – but positive cooperation. Peace through law is the condition necessary for cooperation, trust and creativity. It is the necessary condition for the flourishing of all life on the planet.
These observations are as true of international law as they are for any other body of law. The very origins of international law lie in the struggle to regulate resort to force. To date, a limited right to use force in cases of self-defence or when authorised is considered consistent with a moral order built on peace. Those contributing to international law have ever since struggled between the poles of opening the law to greater acceptance of violence and retaining restrictions and even building on them. This centuries-old debate has reached us today in the form of legal prohibitions on the use of force that count among international law’s highest norms as against a continuing effort to develop new legal formulas reducing the restrictions on certain States and actors in attaining their preferred goals. Three of these doctrines have been examined here – inherent right/imminence, terrorist attack/armed attack, and unable/unwilling – and found to be inconsistent not only with the general goal of greater peace but even with the more limited ends that they espouse.
The reason non-State actors are or have been considered the enemy is because they use violence in defiance of fundamental law, the very law the three pernicious doctrines undermine. The three doctrines have many flaws as a basic legal matter: they ignore the plain meaning of express treaty terms; they ignore legal presumptions that bear on accurate interpretation; they ignore the status of the prohibition of force as ius cogens; they ignore the long history of struggle to create positive law norms restricting force; and they ignore the data on the ineffectiveness of military force for most goals other than simple self-defence, data which goes to the heart of determining the necessity of using force. Despite these flaws, the three doctrines of self-defence examined here make little common sense when seen as a part of a general rule of international law applicable to all. The doctrines emerged to justify uses of force by the US and UK after the fact. When used to justify force by other States, the deep flaws are plain even to those sympathetic to them.
In response to the spectre of wider rights to use force, proponents of the three doctrines point out that the fear of military retaliation by the UK or US prevents the dangers predicted from materialising. In a world of military power imbalance, fair and equal understanding of the rules is not needed. The reason law has power, however, is the very fact it applies generally. Law does not depend on physical or military strength. It does not depend on divine revelation accessible to the enlightened or blessed among us. It does not depend on being the friend or relative of a national leader. We develop law through reason, drawing on our understanding of the natural world, as well as transcendent inspiration engendered by beauty or faith. This approach to law has led to the most fundamental principle of law, one uncontestably held universally: the principle of fairness. In the West, Aristotle is credited for defining fairness as the treatment of like cases alike. Fairness means the subjects of the law are treated as equal before the law. Sovereign States are the principal subjects of international law. If one has the right to go to war to pre-empt an attack or because another State is unable or unwilling to do something then all States have the same right.Footnote 366
The three doctrines analysed in this chapter are exceptionalist views of the law. They have been developed to justify unlawful uses of force by leaders of States with major militaries and programmes of research into new weapons technology. These are States that have also enjoyed stature and prestige in the world for their commitment to the rule of law. The three doctrines paper over the law violations that gave rise to them. On close analysis, they make nonsense of the general prohibition on the use of force. If every government is free to decide to use force on the basis of any of these propositions, the use of force is for all practical purposes unrestricted. Without controls on violence, international law is no longer law. Instead of pouring effort into building such doctrines, the current generation of legal scholars is overdue to take up the progressive development of the law of peace. No advances have been made in this area since the drafting of the UN Charter in 1945 and the discernment at that time that significant violations of Article 2(4) violate a ius cogens norm.
Legal scholars interested in advancing the law of peace have clear challenges. Among them is the need to develop global law enforcement, not mere clearing houses for warrants like Interpol. A robust global law enforcement institution is essential and must have the best cybercrime fighting capacity possible and a thorough grounding in international law. The world also requires the revival of the practice of peaceful settlement of disputes, particularly a return to the ability to mediate an end of conflicts and a restoration of interest in the compulsory jurisdiction of the International Court of Justice. Finally, a new substantive prohibition on civil war is needed. The thinking that encourages the taking up of arms to overthrow dictatorial regimes as moral crusading can be replaced with the model of waging peaceful campaigns of non-violence.
These goals are consistent not only with the prohibition on the use of force, but with the legal presumption of peace, and with the human right to life. These are all norms the international community has preserved through the assaults of realists, humanitarian interventionists, and other militarists. It should be celebrated that these norms have been preserved.Footnote 367 They can also be renewed and re-prioritised in communities locally and globally. They are worthy of the efforts of the international legal community and the ideal of the rule of law.
This returns the discussion to the beginning and the targeted killings with military force in Syria of ISIS members Reyaad Khan and Junaid Hussain by the UK and US. The UK Prime Minister said that the killing of Khan and the people near him with drone-launched missiles was an exercise of the UK’s ‘inherent’ right of self-defence. In attempting to justify the killing, Prime Minister Cameron was reaching back to 1958 and the claim that States may use force in self-defence on the basis of necessity, even when no armed attack occurs. The claim is in clear conflict with the terms of the Charter and the peremptory norm prohibiting the use of force. States may invoke an exception to the prohibition for self-defence if the exercise of self-defence meets the terms of Article 51, which include the condition that an ‘armed attack occurs’.
The US issued no specific justification for killing Hussain. Nine months after the attack, however, State Department Legal Adviser Brian Egan claimed a right of the US to use military force to kill people in States that are ‘unable or unwilling’ to control terrorists active within their border.Footnote 368 This is as close as the US has come to issuing a justification. After 9/11, the US attempted to argue it was in a ‘global war’ with terrorism. The Obama administration abandoned that position to argue the US is involved in a worldwide ‘armed conflict with Al-Qaeda and associated forces’.Footnote 369 Both claims were built on the series of terrorist attacks Al-Qaeda members have carried out against the US starting in 1993. As terrorist attacks, however, they have been intermittent, often low-level, and unconnected with a State sponsor. They have been crimes, not armed attacks triggering the right of self-defence. Even the 9/11 attacks most likely lacked the requisite link to Afghanistan to support the exercise of self-defence against that State.Footnote 370 If Afghanistan was responsible, the use of force has been beyond anything necessary or proportionate to the 9/11 attacks.
Al-Qaeda and ISIS are enemies, which may explain why Egan proffered a new justification in 2016 for military attacks on ISIS members, like Hussain. In saying, however, that Syria is ‘unable’ or ‘unwilling’ to control ISIS and that that judgment gives rise to the right to attack individuals, Egan had to ignore critical facts as well as the law. At the time of Hussain’s killing, Syria was fighting strenuously to defeat ISIS. Syria was clearly not ‘unwilling’ to counter it, and Syria might have had more success – been less ‘unable’ – had the US not been actively supporting non-State actors fighting to bring down the Syrian government and thereby incidentally reducing the Syrian capacity to combat ISIS. These are the facts. On the law, the case is just as weak. The claim extrapolates from the State responsibility principle that a non-State actor controlled by a State incurs the State’s own responsibility. An armed attack that can trigger Article 51 will be attributed to a State if carried out by a non-State actor controlled by the State. Syria does not control ISIS, even if it could be shown that ISIS had carried out the requisite attack on the US, a subjective American judgment that Syria is now responsible for ISIS attacks because it is unable or unwilling to control ISIS does not change the attribution principles. The principles of attribution are embedded in the very structure of international law and may not be simply ignored, however complex or inconvenient the duty of compliance. Law is often complicated and inconvenient. In this area, however, complexity offers no excuse for failing to comply. There is a straightforward alternative to the risk of violating the law: when in doubt find non-lethal alternative responses.
Attribution principles are general principles, and as such do not change based on contrary State practice. The UK and US may wish to hold Afghanistan or Syria responsible in order to have the legal basis for military attacks against them, but it needs to show control by those States of non-State actor conduct. Equally, the UK and US are barred from claiming that they may substitute the unable/unwilling concept for Syrian consent to kill Khan and Hussain.
In violating the prohibition on the use of force in the killing of these men, the UK and US have violated a ius cogens norm. It is a durable norm that will not fade under the pressure of contrary practice. Yet, neither will the scourge of terrorism. Success against terrorism has been won through upholding the rule of law, using law enforcement measures, and building successful communities – expanding the options for peace, not the excuses for war. Some may find these conclusions radical or even utopian. They are likely counter-cultural, but beyond that are no more than the findings which follow from comprehensively assessing the theory, law and facts of self-defence against non-State actors.
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