1.1.1 International Humanitarian Law

International humanitarian law was specifically designed to determine who and what is protected in armed conflict. A contrario, it therefore indicates which targets are legitimate. Among the treaties that constitute the core of IHL, the primary role is definitely played by the four Geneva Conventions for the Protection of War Victims of 1949 and their Additional Protocols of 1977. More states are parties to the GCs (196) than to the UN Charter of 1945 (193).Footnote ⁴ This universal acceptance means that all the regulations of these conventions qualify as customary law.Footnote ⁵

As regards legitimate targets, the GCs did not supersede, but only complemented (and even that to a fairly small extent) the regulations of, for example, the Convention respecting the Laws and Customs of War on Land and its annex, Regulations concerning the Laws and Customs of War on Land, both of 1907.Footnote ⁶ Consequently, in this area the APs are much more important than the GCs, because they contain both the norms on protection of specific categories of persons and objects, and the law on legitimate attacks.

Compared to the GCs, the APs have significantly fewer ratifications: 174 for AP I and 169 for AP II, respectively. Several states that currently are or recently have been involved in an armed conflict (and thus they can be qualified as States whose interests are specially affectedFootnote ⁷ with regard to the emergence of customary norms of IHL) have not ratified the AP I or II.Footnote ⁸ Importantly, there are often discrepancies between the practices of these states and the norms codified in the APs. This is crucial, because the case law of the International Court of Justice suggests that it is precisely the practice of states, not parties to a given treaty, that has particular impact on the assessment of whether or not the treaty regulations can be considered part of customary law.Footnote ⁹ It is therefore arguable whether the regulations of the APs in their totality now have the status of customary law, and, in my opinion, there are good reasons to believe that it is not the case.

As a result, while a large proportion of the regulations in the APs is considered customary law,Footnote ¹⁰ the APs in their totality are not applicable to all subjects of international law as customary law.Footnote ¹¹ This is particularly true with regard to AP I,Footnote ¹² because many states that have decided to ratify it have submitted reservations or declarations of interpretation concerning, for example, the definition of combatant (status of members of irregular forces and the obligation to distinguish themselves from the civilian population), the presumption of civilian status of a person or object, the definition of a mercenary, the prohibition of reprisals, the principle of proportionality, and the obligation to undertake relevant precautionary measures before and during attack.Footnote ¹³ The same issues have prevented some states from ratifying AP I.Footnote ¹⁴

As a result, it is still important to consider whether an armed conflict should be viewed through the lens of the GCs and the AP I or II, or whether the GCs alone apply. This is particularly important with regard to non-international armed conflicts, which – depending on the circumstances – either fall solely under the regulation of Article 3 GCs, or are also governed by the norms of AP II. It should be noted that AP II is quite modest in extent, having only twenty-eight articles, of which ten are final provisions. This is hardly impressive compared to GC IV on the protection of civilian persons in time of war, with its 159 articles (of which 10 are also final provisions) – and this is not counting the annexes. To recapitulate: in a great majority of situations that qualify as armed conflict,Footnote ¹⁵ the only applicable laws are the select few provisions of IHL treaties, modest as they are in both volume and content.

Beside treaty provisions proper, customary norms of IHL apply in each armed conflict.Footnote ¹⁶ Customary law is particularly important when it comes to non-international armed conflict, due to the above-mentioned scarcity of treaty regulations in this regard, and in armed conflict where international organizations are involved, taking into account the way non-state parties to armed conflicts are bound by IHL.

Customary law on the conduct of hostilities in armed conflict is not itself fragmented. There is just a single body of norms, although it is influenced by many branches of international law. Custom emerges where a general uniform practice (usus) is accepted as law (opinio juris).Footnote ¹⁷ This is why, in my opinion, customary norms regarding the use of lethal force in armed conflict cannot vary depending on the lens of a specific branch of law applied to their analysis.Footnote ¹⁸ In other words, no customary norms on legitimate targets and methods of attack can exist that would be contradictory to one another.

The International Committee of the Red Cross (ICRC) undertook the task of identifying customary international norms of IHL in its 2005 Study on Customary International Humanitarian Law (hereinafter: Study on Customary IHL).Footnote ¹⁹ The ICRC regularly updates the database on state practice to enable the verification of the status of each norm.Footnote ²⁰

A lot of criticism has been directed at the Study on Customary IHL, focusing mostly on the methodology that underlies the document.Footnote ²¹ The problematic issue is that the ICRC, when it accepted that there is sufficient opinio iuris to attest to the existence of the norms, did so in reliance on documents adopted by international organizations (including non-governmental organizations) and declarations of non-state armed groups. Furthermore, the decisive factor in the ICRC’s assessment of state practice is official declarations of states and documents such as military manuals (often comprising both legal and political elements), rather than actual conduct of states’ organs during armed operations.Footnote ²² On the one hand, it must be noted that the custom is built up … by practice, and not only by a promise of practice or by opinions as to its necessity.Footnote ²³ On the other hand, in certain situations the existence of the norm is not challenged even when the norm itself is breached.Footnote ²⁴ In my opinion, both the practice and the official statement(s) of the state commenting on its practice must be analysed in order to clearly indicate a particular customary norm.

Finally, according to the Study on Customary IHL, the norms applicable to international and non-international armed conflict appear to be nearly identical, a claim that is vigorously rejected by several states and by part of the doctrine.Footnote ²⁵

In view of the criticism of the Study on Customary IHL, its conclusions must be approached with caution – but they should not be disregarded. There are many years of work behind this document, numerous highly regarded experts have made their contributions to this effort, and it is supported by the ICRC, an independent humanitarian organization with special status under international law. Under the Statutes of the International Red Cross and Red Crescent Movement, it is the responsibility of the ICRC to work for the faithful application of international humanitarian law applicable in armed conflict and to take cognizance of any complaints based on alleged breaches of that law, and to work for the understanding and dissemination of knowledge of international humanitarian law applicable in armed conflict and to prepare any development thereof.Footnote ²⁶

The ICRC exercised these rights, for example, by launching an effort to develop more precise definitions of the notions used in the GCs and APs, such as ‘direct participation in hostilities’ (Article 3 GCs, Article 51(3) AP I, Article 13(3) AP II) and ‘civilian’ in non-international armed conflict (Article 13 AP II). After years of consultations with experts, the ICRC published its Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law (hereinafter: ICRC Interpretive Guidance).Footnote ²⁷ The document is not binding and falls under the umbrella of soft law, with all its attendant consequences.

ICRC Interpretive Guidance has been wildly controversial, to the point that allegedly some of its authors, after having invested years of work (2003–8) in the effort, have opted not to have their authorship acknowledged in the document.Footnote ²⁸ Yet again, given the unique status of the ICRC and the uncontested significance of the analytical insights and arguments presented in the ICRC Interpretive Guidance, it is necessary to invoke it when interpreting the notions that are crucial for consideration in this monograph.

Other soft law instruments that may have an impact on the status and scope of application of IHL norms include the resolutions of intergovernmental organizations,Footnote ²⁹ as well as resolutions and guidelines issued by recognized expert institutions, for example the Institute of International LawFootnote ³⁰ and the International Institute of Humanitarian Law.Footnote ³¹

1.1.2 International Human Rights Law

Nowadays, it is widely accepted that in an armed conflict, IHRLFootnote ³² applies beside IHL.Footnote ³³ IHRL is designed to safeguard rights (generally) vested in natural personsFootnote ³⁴ and protect these persons vis-à-vis organs of a state and, in some cases, against organs of international organizations.Footnote ³⁵ It protects natural persons from legally unjustified interference in specific spheres, but also forces the organs to take active steps to protect human rights.

Certain human rights – freedom from torture, for example – while also enshrined in specific treaties, have gained the status of customary laws and even peremptory norms.Footnote ³⁶ Given that numerous states have not ratified the fundamental human rights conventions, this is vital because it means that certain prohibitions of violating human rights are binding on these states by virtue of their status as customary law.

While IHRL allows for the suspension of certain norms in extraordinary circumstances, certain rights – the right to life,Footnote ³⁷ and the prohibition of torture and inhuman treatmentFootnote ³⁸ – are non-derogable. Incidentally, in my opinion, they are also crucial in the determination of legitimate targets as even during an armed conflict, the states may not suspend their obligation to uphold these rights.Footnote ³⁹

The International Court of Justice,Footnote ⁴⁰ the European Court of Human Rights,Footnote ⁴¹ the Inter-American Commission on Human Rights, and the Inter-American Court of Human RightsFootnote ⁴² all have confirmed that human rights protection standards must be upheld even in armed conflict situations, and have noted on several occasions that states must uphold human rights when they are engaged in hostilities outside of their own territory.Footnote ⁴³

Nonetheless, several states – notably the United States and Israel – maintain that they are not bound by IHRL in armed conflict, especially when the conflict is taking place beyond their borders.Footnote ⁴⁴ This is an attempt on the part of these states to prevent the emergence of a customary norm upholding the exterritorial application of human rights in armed conflict, or, failing that, to secure the status of persistent objectors should the norm ultimately emerge.Footnote ⁴⁵

This position is quite understandable: IHL and IHRL appear to be so different that their simultaneous application appears impossible (or very difficult, at best), especially with regard to the selection of legitimate targets and the manner of attack in armed conflict. While ‘how to kill your fellow human beings in a nice way’ is a catchy, tongue-in-cheek phrase describing the role of IHL, such considerations are in fact completely inadmissible in any discussion of human rights.Footnote ⁴⁶ IHRL is immensely restrictive with regard to killing human beingsFootnote ⁴⁷ and only allows for this option in extraordinary circumstances when it is strictly unavoidable in order to protect life.Footnote ⁴⁸ In effect, IHRL precludes the option of killing a person or destroying an object purely on the basis of their status,Footnote ⁴⁹ and any operation must be planned to minimize the risk of death, injury, or destruction.Footnote ⁵⁰ Compared to IHRL, IHL gives combatants a relatively free hand in destroying certain specific objects (Article 52(2) AP I) and killing persons who fit into certain specific categories (e.g. Article 43 AP I). Furthermore, the underlying belief in IHL is that the reason for the use of force is immaterial to the assessment of whether a particular attack is lawful.Footnote ⁵¹ In contrast, such assessment under IHRL must involve the question of legitimacy of the use of force.Footnote ⁵²

Given the manifest discrepancies between the principles governing these two branches of law, it is necessary to determine which norms apply to a specific situationFootnote ⁵³ and how their implementation will play out in practice.Footnote ⁵⁴ Yet it is crucial to bear in mind while engaging in this process that most states ratified the fundamental conventions of both IHL and IHRL,Footnote ⁵⁵ and thus it stands to reason that they neither perceived them as fundamentally irreconcilable nor wished to deprive any of them of their impact.

The case law of the International Court of Justice suggests that a decision to attack a person in an armed conflict must be governed by IHL before IHRL, as evidenced by the 1996 advisory opinion on the legality of the threat or use of nuclear weapons, which includes the following passage:

I think that this wording does not suggest that the legitimacy of killing a specific person is determined solely by IHL, but rather that IHL cannot be disregarded in this determination. Article 15(2) ECHR should be interpreted in a similar manner. While the Convention stipulates that a state of public emergency is not a sufficient reason to derogate from the obligation to protect the right to life, in Article 15(2) it makes the reservation that ‘deaths resulting from lawful acts of war’ are an exception to this rule. Formal declarations of derogation are very rare with regard to this norm of the Convention.Footnote ⁵⁷ Yet, in my opinion, this is not an argument against using the norms of IHL in the assessment of certain actions.Footnote ⁵⁸

Interestingly, the International Court of Justice in its subsequent rulings steered clear of the term lex specialis, the use of which had been justly criticized.Footnote ⁵⁹ A single armed conflict may involve a range of situations that require the application of differing standards of the use of force. For instance, there is no doubt that IHL applies to attacks against specific categories of persons in direct hostilities, but in a territory under a state’s control the use of force should be governed by the principles that apply to use of force by law enforcement – that is, in the spirit of IHRL.Footnote ⁶⁰ In consequence, soldiers must be able to apply different standards depending on the specific situation.Footnote ⁶¹ Even so, borderline scenarios are unavoidable, for example when social unrest and protests against the occupying power turn into regular hostilities.Footnote ⁶²

It is therefore impossible to determine in abstracto which branch of international law – IHL or IHRL – should serve as lex specialis, and which as lex generalis, and thus which should apply to each and every situation arising during an armed conflict.Footnote ⁶³ The standards that apply in a given situation always depend on the specific circumstances of that situation. The two branches of law are complementary,Footnote ⁶⁴ a claim which is further supported by the direct inter-references in the fundamental treaties of IHL and IHRL.Footnote ⁶⁵ Furthermore, IHRL has an impact on the interpretation of the norms of IHL and vice versa,Footnote ⁶⁶ which is in line with the general rules of treaty interpretation enshrined in Article 31 of the Vienna Convention on the Law of Treaties of 1969, according to which in a process of interpretation of a treaty ‘any relevant rules of international law applicable in the relations between the parties’ should be taken into account.

1.1.3 International Criminal Law

Norms of ICL criminalize the violations of the norms of IHL and IHRL, and lay down precise principles of responsibility for these violations. It thus stands to reason that criminal courts would invoke the relevant provisions of IHL and IHRL when interpreting the regulations that apply to specific international crimes. After all, no war crime can be committed without violating IHL. Yet an analysis of statutes and judgments of international criminal tribunals indicates that, often, the norms expressed therein differ from the norms enshrined in the GCs and APs.Footnote ⁶⁷

These differences often arise from the specific purposes for which criminal tribunals are established, which is to assign criminal responsibility to individual persons and to hold these persons culpable beyond any doubt. This requires sharper formulations to remove any doubt that, for example, there was an armed conflict in a given situation, or that a specific person was fully aware of the consequences of their actions.

The proviso must be made here that the status of customary law as a source of ICL is debatable in view of the principle of legality, and this prevents customary law from being accepted as a sole basis for individual criminal responsibility due to its insufficient precision.Footnote ⁶⁸ Interestingly, the Rome Statute does not directly list customary law among the laws the ICC applies, but at the same time allows for the application of ‘principles and rules of international law, including the established principles of the international law of armed conflict’ and, in the context of investigating general principles of law derived from national laws of legal systems of the world, ‘international law and internationally recognized norms and standards’.Footnote ⁶⁹ On the one hand, this wording may be read as a reference to customary law. On the other hand, and more convincingly in my opinion, it may be viewed as evidence of a very cautious approach to customary law as a source of international individual criminal responsibility. This is one of the reasons why (despite the general statement in Article 8(2)(e) concerning penalization of ‘other serious violations of the laws and customs applicable in armed conflicts not of an international character’) efforts were undertaken to adopt amendments to the Rome Statute to criminalize violation of prohibitions of use of certain types of weapons (e.g. poison) and methods of warfare (starvation) in non-international armed conflict (even though these prohibitions, according to the Study on Customary IHL, were already in force by virtue of customary law).Footnote ⁷⁰

The norms enshrined in statutes of international criminal tribunals, as well as the case law generated by these tribunals (alongside the case law coming from national courts) may shape customary law on legitimate targets and methods of attacks. This is vital with regard to non-international conflict, considering the scarcity of treaty regulations that apply to such conflict.

In view of the fragmentation of treaty law regulating targeting, I believe that criminal tribunals have a crucial role to play. By their very nature, they draw on the regulations of various areas of law, and by referencing the case law of other courts and tribunals they work towards the development of uniform standards and elimination of discrepancies.Footnote ⁷¹

1.2.1 Material Scope

International humanitarian law only applies during armed conflict. Recently, an approach has emerged that argues against distinguishing between international and non-international conflicts.Footnote ⁷² Yet the distinction continues to matter, because different treaty norms apply depending on the type of conflict. This includes treaty norms related to legitimate targets and methods of attack.Footnote ⁷³

In international conflicts, the GCs and AP I apply. All armed conflicts between at least two states qualify as international armed conflicts. This includes occupation – that is, a situation when a certain territory is under control of the adversary’s army (Article 42 HR), even if it encountered no armed resistance (Article 2 GC and Article 1(3) AP I).

In non-international armed conflicts (NIACs), Article 3 GC applies, as does AP II, if the armed conflicts take place in the territory of a High Contracting Party between its armed forces and dissident armed forces or other organized armed groups which are under responsible command and which exercise such control over a part of the state’s territory as to enable them to carry out sustained and concerted military operations and to implement AP II. If the group has no such control over territory, or when hostilities involve no armed forces, only Article 3 GC applies.

Whether or not there is an IAC is quite easy to observe; any resort to armed force between states suffices.Footnote ⁷⁴ Yet the case law of the International Criminal Tribunal for the former Yugoslavia suggests that a certain level of intensity of military operations must occur for the situation to qualify as an IAC.Footnote ⁷⁵ Furthermore, the deployment of armed forces must be deliberate. If the armed forces of one state enter another state by mistake – as was the case in 2007 when Swiss troops entered the territory of Liechtenstein – no armed conflict exists.

Under Article 1(4) AP I, the category of IAC also includes ‘armed conflicts in which peoples are fighting against colonial domination and alien occupation and against racist régimes in the exercise of their right of self-determination, as enshrined in the Charter of the United Nations and the Declaration on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the Charter of the United Nations’.Footnote ⁷⁶ This wording was introduced with specific conflicts in mind,Footnote ⁷⁷ and the emotionality of the language was to serve as a guarantee that Article 1(4) AP I would find application very rarely, if at all.Footnote ⁷⁸

The expanded understanding of IAC under AP I was heavily criticized because it introduces a subjective element that belongs to ius ad bellum;Footnote ⁷⁹ the classification of a conflict is predicated upon a specific objective of the hostilities. It is therefore unsurprising that many states submitted declarations on interpretation regarding Article 96(3) AP I, under which AP I applies automatically to a conflict defined in Article 1(4) AP I if the authority representing a people involved in the hostilities submits a unilateral declaration addressed to the depositary of the Protocol. These declarations on interpretation pertain to the following issue: who can be recognized as ‘the authority representing a people’ (typical restrictions refer to the need for prior recognition by an intergovernmental regional organization or true representation of a people),Footnote ⁸⁰ They serve to limit the possibility of the application of Article 1(4) AP I or, failing that, to have predominant influence on how this regulation is applied. Yet characteristically, the sole unilateral declaration submitted so far to Switzerland (the depositary of both the GCs and the APs) under Article 96(3) AP I is a declaration by the Polisario Front dated 21 June 2015.

In the case of NIAC, a distinction must be made between armed conflicts and ‘situations of internal disturbances and tensions, such as riots, isolated and sporadic acts of violence and other acts of a similar nature’, which are not considered armed conflict.Footnote ⁸¹ Paradoxically, the bar for application of NIAC law is therefore set higher than for application of IAC law,Footnote ⁸² even though the absence of definition of NIAC in Article 3 GCs was specifically designed to maximally broaden the scope of its application.Footnote ⁸³

The ICTY’s case law suggests that a NIAC exists when there is ‘protracted armed violence between governmental authorities and organised armed groups or between such groups within a State’.Footnote ⁸⁴ Several conclusions can be drawn from this statement. Firstly, a NIAC can take place not only between armed forces and an armed group, but also in a situation that does not involve armed forces at all and the hostilities take place solely between non-state actors.

Secondly, the intensity of hostilities should be assessed taking into account their duration – since the Tribunal used the wording ‘protracted armed violence’.Footnote ⁸⁵ This renders it difficult to determine the starting point of a NIAC. Other factors that are cited in case law and literature as determinants of the existence of armed conflict include, for example, use of armed forces rather than the police; number of troops involved in the conflict; collective character of hostilities; their frequency and seriousness; number of casualties; scale of displacement of civilians and of detention of fighters; the extent of destruction; use of heavy weaponry; spread of hostilities over territory; whether the conflict has attracted media, NGO’s and the UN SC’s attention and if any resolution on the matter has been passed; whether those fighting considered themselves bound by IHL; and signing of ceasefire agreements.Footnote ⁸⁶ If a certain level of intensity of hostilities is required, single targeted attacks (e.g. the practice of targeted killings)Footnote ⁸⁷ are precluded from triggering the application of IHL. However, it can also be convincingly argued that a series of attacks carried out by one group should be treated as a whole, which would qualify the level of conflict as sufficient across the areas where hostilities took place (or are taking place), even if these areas are located at a considerable distance from one another.Footnote ⁸⁸

Thirdly, a non-state actor involved in hostilities must be sufficiently organized to be considered a party to the conflict, since Article 3 of the GCs refers to ‘each Party to the conflict’.Footnote ⁸⁹ This means the ability to plan and carry out military operations.Footnote ⁹⁰ The following factors may reflect sufficient organization: a clear command structure; the ability to impose and enforce discipline; a command headquarters; operations that involve a larger number of units; recruitment and training of combatants; control over territory; speaking on behalf of a group; working strategy and tactics; acquisition, transportation, and distribution of weapons; adoption of formal codes of conduct inside the group; and negotiation and execution of agreements.Footnote ⁹¹ This also implies, in my opinion, that cases of one-sided violence against civilians – whether perpetrated by armed forces or non-state armed groups – never qualify as armed conflict, regardless of type, due to the absence of another party to the conflict. It is only when state authorities commence hostilities against a non-state armed group, or when two or more non-state armed groups take up hostilities against each other, that the possibility of escalation to an armed conflict arises, and such conflict may be determined to exist due to the existence of at least two clear parties thereto.

Case law suggests that objective reasons, rather than subjective opinions of the parties to the (alleged) conflict, determine whether a conflict as such exists.Footnote ⁹² The motivations and goals of the belligerents have no bearing on the application of IHL. As a result, situations where hostilities fall into the category of terrorism may still qualify as armed conflict, with the consequent application of IHL.Footnote ⁹³ In general, IHL attempts to render the conditions that qualify certain events as armed conflicts as objective as possible, although in borderline cases the opinion of the parties may prove decisive in the determination of whether a conflict in fact exists.

It is possible to recognize, either explicitly or silently, a non-state party as a belligerent, which triggers the application of the entire international law of armed conflict.Footnote ⁹⁴ This recognition, however, is very rare, because it is (wrongly, in my opinion) perceived by states as a symptom of weakness and a concession.Footnote ⁹⁵ Also, it might encourage (or even provoke) external support for the non-state party.Footnote ⁹⁶ From the perspective of the state, another drawback is that recognition of belligerency means that members of the non-state armed group cannot be brought to justice only for their participation in hostilities. However, there is a mutual benefit to recognizing a non-state party to an armed conflict as a belligerent. Namely, it renders the persons participating in the conflict on either side eligible for prisoner-of-war status. Failing that recognition, even members of the armed forces cannot claim this status when captured, which means that either party tends to fight until the end, knowing that no one can expect any mercy if captured.

Another controversy involves the status of a conflict taking place in the territory of one state between the armed forces of another state and a non-state party. In my view, as long as the intervention is directed not against the armed forces of the state but rather against a non-state armed group, the conflict is non-international, despite occurring in the territory of another state.Footnote ⁹⁷

In contrast, in its commentary on Article 2 GCs, the ICRC posits that the use of armed force against the territory of another state, its civilian population, or its civilian objects, should be treated as an IAC.Footnote ⁹⁸ Moreover, even if the hostilities are directed against a non-state armed group, but with no clear consent from the state’s authorities, the situation qualifies as an IAC in terms of protecting the civilians and at the same time as a NIAC in terms of operations directed against the non-state participant of the conflict.Footnote ⁹⁹ The ICRC is not a proponent of creating a new category of transnational conflicts – that is, conflicts that become internationalized by the very fact of outside interventionFootnote ¹⁰⁰ – but it accepts that it is possible for several conflicts of different natures to occur simultaneously in the territory of one state.Footnote ¹⁰¹

In my opinion, the ICRC’s approach is rooted in the inaccurate belief that the laws applicable to IAC protect the civilian population better than those applicable to NIAC. However, an even better standard of protection is offered by international human rights law used as an instrument of interpretation of the norms of IHL that pertain to NIAC. As was pointed out earlier, IHRL is much more restrictive than IHL as regards attacks against persons.

Furthermore, the solution proposed by the ICRC is in my view impractical. The principles on attacking military targets are closely tied to the principles of protection of specific categories of persons and objects. The definition of a civilian person is different depending on the type of conflict (an international or a non-international one) and it is constructed in opposition to the notions of combatant (IAC) or member of the armed forces and member of an organized armed group (NIAC) respectively. Similarly, the definition of a civilian object is negative as it encompasses all goods which cannot be qualified as military objectives, a notion that can be understood slightly differently depending on classification of the conflict. It is therefore hardly possible to apply at the same time the norms of IAC to protect civilians and the norms of NIAC to determine the legitimacy of targets and attacks.

Application of the current IHL is clearly limited to armed conflicts. Therefore, in my judgement, its norms cannot be applied to singular crimes or acts of terrorism,Footnote ¹⁰² which is noted in some of the declarations/reservations submitted by states upon ratification of the GCs and APs.Footnote ¹⁰³ It is therefore very surprising that states are now making references to IHL (rather than IHRL) when discussing the principles by which they are bound when engaging in anti-terrorist or police operations.Footnote ¹⁰⁴

1.2.2 Geographical Scope

In terms of geographical scope of conflict, in international conflicts IHL applies throughout the territory of each state involved in the conflict (Article 49(2) AP I) as well as in the territories within the jurisdiction of other states (with the exception of neutral states, as long as they continue to meet the relevant requirements)Footnote ¹⁰⁵ and outside the jurisdiction of any state (e.g. in the open sea and in space),Footnote ¹⁰⁶ if this is where hostilities take place.

Article 49(2) AP I stipulates that its provisions ‘apply to all attacks in whatever territory conducted, including the national territory belonging to a Party to the conflict but under the control of an adverse Party’. The application of IHL is therefore not limited to the combat zone.Footnote ¹⁰⁷

It is immaterial ‘where’ hostilities are taking place; instead, it is the ‘when’ that matters.Footnote ¹⁰⁸ This is interesting to note, for example, regarding the armed conflict that began in 2001 between the USA and its allies against Afghanistan, as well as the conflict that began in 2003 between the USA and its allies against Iraq: the impact of involvement in the armed conflicts was hardly felt at all in the territory of the USA and most allied states. Yet Afghani/Iraqi forces had the rights under IHL to conduct attacks in those territories, and the reason they did not was technical difficulty and not legal obstacles.

In the case of NIAC, Article 3 GCs only requires the conflict to begin (‘occur’) in the territory of a state that is party to the GCs; there is no requirement for the conflict to be limited to one state.Footnote ¹⁰⁹ Conflict with an armed group may – and indeed nowadays often does – take place across the territories of several states.

In a NIAC, IHL applies throughout the territory of the state party to the GCs or AP II in which the conflict occurred.Footnote ¹¹⁰ There have been voices suggesting that the application of IHL should be limited to the combat zone.Footnote ¹¹¹ Yet in any armed conflict, given today’s technical progress, hostilities may move quite quickly into another region, in which IHL should then apply. Furthermore, in a specific limited area, force may be used not against the members of the party to the conflict but, for example, against protesters or common criminals, in which case IHL is not applicable due to the absence of hostilities that trigger its application. The case is similar in IAC where an occupied territory can be the arena of both hostilities (if fighting with the opposition breaks out) and of police operations (to quash unrest). Thus, if hostilities occur in the territory of a state, in my opinion, IHL applies throughout this state, and temporary absence of hostilities in a specific limited area has no impact on the geographical scope of IHL’s application.Footnote ¹¹²

If a conflict spills over to the territory of a neighbouring state, IHL applies across the area controlled by the parties to the conflict (i.e. not necessarily across the entire territory of the state into which the hostilities moved in whole or in part).Footnote ¹¹³ In theory, this means that the geographical scope of IHL might spread across the entire world if an armed group operates in many states. This is precisely the justification for the above-mentioned practice of targeted killings. It is argued that the armed conflict with Al-Qaeda and its allied forces triggers the application of IHL to targeting persons, and, in consequence, persons can be eliminated on the basis of their status rather than conduct, as stipulated by IHRL.Footnote ¹¹⁴ This leads to abuse of law, for example circumventing the limitations of IHRL or the ban on the use of force in international relations, and thus attempts have been made to curb this application of IHL by emphasizing the need to show the connection between the target and the armed conflict. This connection may be demonstrated by proving geographic proximity of the target to the theatre of operations, level and nature of the military operations in the targeted area, and the connection between the target and the conflict.Footnote ¹¹⁵

As regards the protection of objects, it should be noted that their location in the arena of military operations alone does not mean that they can be destroyed. IHL requires verification in each case of whether the object is a military objective, and allows the object’s destruction/capture/neutralization only once this verification proves positive.

1.2.3 Temporal Scope

Application of IHL begins at the moment the armed conflict comes into existence (Article 6 GC IV; Article 3(a) AP I; Article 3 GCs). As regards IAC, which is taken to occur when any hostilities at all take place between states, IHL should apply from the moment the first shot is fired, the first person is detained, or the first part – however tiny – of the territory of another state party to the conflict comes under occupation.Footnote ¹¹⁶ As regards NIAC, hostilities must reach a certain level of intensity to become recognized as an armed conflict, and thus for the application of IHL to be triggered. There may be, for a time, a certain lack of clarity as to whether IHL should apply.

Application of IHL in general, and of its principles on attacking military objectives in particular, in an IAC should end with the ‘general close of military operations’ (Article 6(2) GC IV; Article 3(b) AP I).Footnote ¹¹⁷ In a NIAC, it should end with ‘the end of the armed conflict’ (Article 2(2) AP II). Today armed conflicts rarely end with a formal peace accord or ceasefire, which (in theory) could indicate a specific date and time that end the application of IHL.Footnote ¹¹⁸ The conflicts of today percolate over time; they die down and then flare up again. This creates an ever-spreading grey zone in which it is unclear whether or not IHL continues to apply.

As regards the IHL norms that indicate potential legitimate targets and methods of attack, it is noteworthy that they apply only until the moment of gaining actual control of an area, at which point it is no longer necessary to determine what should be destroyed and who should be eliminated from fighting. In theory at least, from that point onward the party to the conflict has enough power in this area to requisition buildings and equipment of military significance if needed (e.g. Article 46 HR), and to intern the persons who are considered a threat (Article 79 GC IV).

1.2.4 Personal Scope

In light of the norms on individual criminal responsibility laid down in the GCs (Articles 49 GC I, 50 GC II, 129 GC III, 146 GC IV) and AP I (Articles 85–8), it appears that the obligation to respect IHL is incumbent not only on states but also on their citizens (whom the states bind to these norms by ratifying the treaty). Footnote ¹¹⁹ Whether or not IHL is binding on non-state armed groups and intergovernmental organizations – and, if so, to what extent – is unclear.

As for non-state armed groups, their obligation to respect IHL is mentioned in Article 3 GCs (‘each Party to the conflict’) but not in AP II.Footnote ¹²⁰ Several other treaties (for instance, the 1954 Convention for the Protection of Cultural Property in the Event of Armed Conflict – Article 19(1)) impose obligations not only on states but also on non-state parties to a conflict.Footnote ¹²¹

The following arguments are used in support of the view that non-state armed groups are indeed bound by IHL.Footnote ¹²² Firstly, if non-state armed groups conduct military operations in the territory of a state, they are subject to that state’s sovereign power (even if this is precisely what they are opposing) and thus they are bound by the law applicable in that state, including international law.Footnote ¹²³ The same holds true for citizens of a state party to IHL treaties who are involved in armed operations outside the territory of their state, including operations orchestrated by intergovernmental organizations (the principle of nationality). This argument has at least two shortcomings. It assumes that non-state armed groups recognize their obligation to respect the law of the state against which they are fighting. Furthermore, this assumption is debatable in light of the obligations that result from IHL but that are interpreted through the lens of IHRL. This is because IHRL (which may have an impact on the principles that apply to identifying and attacking targets in armed conflicts) is not generally horizontal in effect, meaning that there is no obligation to apply it in relations between individuals or other entities.

Secondly, non-state armed groups are bound by IHL (as well as IHRL and ICL) because these branches of law draw heavily from customary law and general principles of law, and thus are binding on any subject of international law.Footnote ¹²⁴ While non-state armed groups are not strictly recognized as such, they are still supposed to meet the requirement of observing customary law, even if they have no opportunity to actively shape it.Footnote ¹²⁵

Thirdly, when a non-state armed group forms a new state, it can be argued that succession takes place with regard to IHL, IHRL, and ICL treaties. This, however, is also debatable, because the principles of treaty succession are not unequivocally clear. There are only twenty-three states parties to the 1978 Vienna Convention on the succession of states in respect of treaties, meaning that the principles enshrined in that convention failed to find general recognition.

Fourthly, an argument can be made that IHL treaties create privileges – which are closely tied to obligations – with regard to third parties whose consent to these privileges and obligations is presumed, meaning that these third parties are expected to observe these treaties. Again, this is debatable. Article 35 VCLT only allows obligations to be imposed on third-party states with their consent expressed in writing. However, the convention only refers to states, and so it may be argued that other principles should apply to non-state actors.

It is also true that few non-state armed groups negate the application of IHL, because it offers them certain favourable solutions.Footnote ¹²⁶ There is a fairly common practice of non-state armed groups issuing unilateral declarations (deeds of commitment) and codes of conduct, or signing agreements dedicated to this issue, in order to express their adherence to the principles of IHL.Footnote ¹²⁷

Each of these theories has consequences in terms of the scope of the applicable law. Customary law and general principles of law are less precise than treaty norms, and thus the obligation to abide by specific rules – those on the legitimacy of attacks, for instance – may be challenged. Succession only makes sense if a new state is actually created in the territory of a state that was party to the GCs or the APs. However, it is accepted consensus today that non-state armed groups are actually bound by IHL and also by IHRL, although the latter only to a limited degree.Footnote ¹²⁸ While there may be doubts as to the technical ability of the non-state party to observe fair trial rules or rules on the conditions of detention,Footnote ¹²⁹ there is no room for doubts as far as the application of the principle of distinction is concerned – and this principle is crucial in terms of deciding on the legitimacy of potential targets in armed conflict.Footnote ¹³⁰

As for intergovernmental organizations, the same argument can be made: as subjects of international law (and, in contrast to non-state armed groups, the fact that intergovernmental organizations have this status is undisputed),Footnote ¹³¹ they are also bound by the norms of IHL and IHRL under customary lawFootnote ¹³² and the general rules of international law.Footnote ¹³³ Additionally, certain intergovernmental organizations have adopted internal regulations to ensure adherence to IHL; this is the case with the United NationsFootnote ¹³⁴ and the European Union, for example.Footnote ¹³⁵ These documents were intended to promote clarity as to the scope of obligations under international law of the armed forces of these organizations (or, more precisely, the armed forces put at the disposal of these organizations), in case an armed conflict should arise. However, no such clarity has been achieved because the regulations are quite general: they include no complete list of obligations that can be derived from customary law, not to mention that the treaties that are binding on specific states.Footnote ¹³⁶ Consequently, the degree to which the norms not specifically listed in the documents adopted by these organizations are binding on them remains open to debate.

When a military operation is launched by a coalition of states, it is extremely difficult to determine which norms on target legitimacy apply.Footnote ¹³⁷ In view of IHL itself, this is not really complicated: according to Article 2 GCs and Article 2(b) AP I, whatever regime is shared by all the participants of the operation will apply.Footnote ¹³⁸ If the USA is party to the GCs but not the APs, and its ally Canada is party to both the GCs and the APs, their joint military operation will only be governed by the GCs and customary law. In practice, Canadian troops will apply the appropriate AP in its entirety as well, because this is what they have been trained to do (but they will not be held responsible for violations of the APs, should they occur). A greater problem arises when one of the members of the coalition categorically eschews the application of IHRL to its armed operations and another one makes it a requirement that IHRL be applied.Footnote ¹³⁹ The dilemma is solved, in my view, by the application of customary law (which is also shaped by IHRL) as long as the state in question is not a persistent objector with regard to a specific customary norm involved.

1.3.1 Humanity versus Military Necessity

IHL rejects the option of total war (which posits that during armed conflict entire societies are involved in fighting one another, and thus everything and everyone must be destroyed if this appears necessary to ensure final victory).Footnote ¹⁴⁰ IHL rejects the assumption that the purpose of the conflict is the total destruction of infrastructure, industry, transportation systems, etc., of the enemy, or the annihilation of the population on the other side of the conflict. Instead, it posits that the purpose is to weaken the military forces of the enemy.Footnote ¹⁴¹ In consequence, IHL does not prohibit attacking anybody actually involved in military operations and anything that directly serves to support these operations.Footnote ¹⁴² This stems from the principle of military necessity. As defined by Article 14 Lieber Code of 1863, military necessity consists in ‘the necessity of those measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war’.Footnote ¹⁴³ If the range of potential legitimate targets were set too narrowly, state security would be threatened and the law would be ignored. If it were too broad, there would be practically no limitations and thus no part of the population would enjoy protection.Footnote ¹⁴⁴ The dilemma is as follows: can any person or object not explicitly protected by IHL be targeted, or should each attack on a lawful target be also assessed in terms of military necessity?

On the one hand, the military necessity is already incorporated in the provisions of the GCs and APs. In these treaties, military necessity appears as a reason to take actions towards persons and objects that are in principle afforded protection,Footnote ¹⁴⁵ and not towards persons and objects that against whom IHL issues no bans on attacks. Thus, there is no need to additionally contemplate the military usefulness of attacking legitimate targets such as combatants or important transport routes.Footnote ¹⁴⁶

On the other hand, the humanitarian aspect of IHL could be emphasized: in each and every case, it merits consideration whether destruction and casualties are absolutely necessary in view of military gains.Footnote ¹⁴⁷ The fact that the GCs and the APs include references to military necessity and military advantage does not mean that in other cases where no such references are made these considerations can be disregarded.Footnote ¹⁴⁸ On the contrary, it means that military necessity should be taken into account in every case, even when the contemplated target is lawful.Footnote ¹⁴⁹ This is emphasized in the Martens Clause, which stipulates that both civilians and combatants ‘remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from the dictates of public conscience’.Footnote ¹⁵⁰ Because the Martens Clause stipulates that the principle of humanity applies in every situation, in my opinion it can be read as prohibiting the unnecessary killing of combatants. Thus, the prohibition enshrined in Article 35(2) AP I of causing unnecessary suffering should be understood to cover, for example, causing anybody pain without military necessity to do so.

In consequence, since total annihilation of the enemy is not the purpose, any plans for attacks against legitimate targets that are possible and allowed but not militarily necessary should be abandoned.Footnote ¹⁵¹ After all, combatants are human beings whose loss will be grieved by their families; destroyed facilities will have to be rebuilt when the hostilities are over. Military necessity justifies the measures that are necessary to accomplish the ultimate objective of the conflict, namely to defeat the enemy – but nothing beyond that objective.

Neither the GCs nor the APs impose an explicit obligation to use the method of fighting that causes least harm, but also neither authorizes killing for no military advantage. Any other interpretation, in my view, would amount to an endorsement of cruelty and a violation of the principle of humanity, which is as fundamental a principle as that of military necessity.Footnote ¹⁵² Not only is this the sole acceptable interpretation of IHL norms in view of IHRL; it is also reasonable given that the military never has unlimited resources to destroy each and every single military objective, regardless of where it is located or how useful it is.

This conflict between military necessity and humanity is sometimes described as the conflict between common sense and idealism.Footnote ¹⁵³ This is very misleading. What the principle of humanity represents is not an unachievable ideal. In fact, it has its roots in part in common sense, and specifically in the self-preservation instinct which discourages people from pushing for endless war that would lead to complete destruction, making way for the annihilation of humanity.

In general, military necessity should not be used to justify violations of IHL, because this undermines its foundations in result.Footnote ¹⁵⁴ However, this view is challenged by the opinion of the International Court of Justice dated 8 July 1996, on the legality of the threat or use of nuclear weapons, which stipulated that in cases where the existence of a state is at risk, the use of weapons (in the scenario contemplated by the Court, nuclear weapons) in violation of fundamental principles of IHL is not ruled out.Footnote ¹⁵⁵

It bears underscoring here that IHL by design never requires more than can be realistically achieved. This is of particular importance with regard to requirements concerning non-state parties. If non-state parties were faced with requirements that were impossible for them to meet, it would likely lead them to disregard this body of law in its entirety (rather than just these impracticable requirements).Footnote ¹⁵⁶

1.3.2 Between Prohibition and Authorization to Use Force

The purpose of IHL is to limit the casualties among those not participating in hostilities and to protect the objects which offer no military advantage if destroyed. The question at the heart of the matter, however, is this: should the absence of an explicit ban on attacks against specific categories of persons and objects be understood as direct IHL-based authorization to pursue these attacks? There is a lot of gravity attached to the answer to this question, particularly in view of the fact that recently states have rediscovered the usefulness of IHL and started invoking it to justify practices such as targeted killings, at the same time categorically objecting to the application of IHRL.Footnote ¹⁵⁷

Allegedly, neither the GCs nor the APs explicitly authorize the use of force towards any category of persons, including combatants. Article 48 AP I requires that the distinction be made between civilians and combatants, but never stipulates directly that operations should be directed against the latter as it is in the case of ‘military objectives’. Furthermore, neither the GCs nor the APs articulate a legal obligation to kill the enemy and/or to destroy the enemy’s objects. On the other hand, it is explicitly articulated – if only to cite the Saint Petersburg declaration of 1868 again – that the object is to weaken the enemy’s armed forces (and thus not to kill the enemy’s troops). The role of IHL was to prohibit certain categories of actions towards certain categories of persons and objects, and not to create a clear authorization. Moreover, the Martens Clause underscores that the absence of an explicit prohibition in treaty law is not automatically equal to authorization in IHL.Footnote ¹⁵⁸ Therefore, it could be argued that to use IHL to give legitimacy to certain types of attacks is a kind of legal perversion.Footnote ¹⁵⁹

On the other hand, the absence of a clear prohibition of killing persons within a specific category could mean the absence of a requirement to demonstrate that the authorizing norm exists (in dubio pro libertate)Footnote ¹⁶⁰. Also, Article 52(2) AP I reads ‘Attacks shall be limited strictly to military objectives’. The category of ‘military objectives’ includes not only objects but also persons with a specific status – for instance, members of the armed forces who qualify as combatants. This is further supported by the fact that phrasing ‘[i]n so far as objects are concerned’ only appears in the second sentence of that section. Moreover, Article 48 AP I stipulates that parties to the conflict ‘accordingly shall direct their operations only against military objectives’ (i.e. against combatants and military objectives). It is true that the above-mentioned Martens Clause underscores that the principles of IHL must always be respected. However, on its own, it cannot serve as a basis for declaring certain actions to be unlawful.

IHL imposes restrictions on armed operations, but is rooted in compromise between the principles of humanity and military necessity, and as such is not intended to preclude the option of armed operations in general. Therefore, in my opinion, certain categories of persons and objects must remain designated as potential targets of deadly force. IHL uses negative definitions to reference civilians (Article 50 AP I) and civilian objects (Article 52 AP I) in IAC, because this determines both whom and/or what is protected and who and/or what can be attacked. Restriction and authorization of attacks really are two sides of the same coin.Footnote ¹⁶¹ If attacking objects in a certain category is clearly acceptable under the law, this means that attacking objects in other categories is prohibited. If the legally allowed options are limited, but armed operations as such are not outlawed, in my view these restrictions must serve as a basis for concluding who and what can be lawfully targeted and attacked.

In consequence, if both in IAC (Article 51(2) AP I) and in NIAC (Article 13(2) AP II) it is prohibited to attack civilians, a contrario it could be concluded that other persons may be attacked.Footnote ¹⁶² If Article 3 GCs and Article 4 AP II stipulate that only those who are not actively involved in the hostilities are protected, then those that do take active part in hostilities have no such protection and therefore may be targeted.

1.3.3 Equality

In IAC, the parties to the conflict have equal rights; in NIAC, that is not the case. For centuries, states have been unwilling to accept any obligations when an internal conflict arises. Any suggestion to regulate armed operations in NIAC was perceived as interference with issues that are by their very nature internal.Footnote ¹⁶³ Rebels were treated as criminals, and therefore – as is traditional – were prosecuted under national rather than international law.Footnote ¹⁶⁴ As a result, the IHL regulations on internal conflicts that were ultimately adopted are hardly numerous and their regulations are general (rather than precise).

It is noteworthy that Article 3 GCs covers the protection of persons taking no active part in the hostilities, and just like AP II it essentially ignores the issue of conducting hostilities against potential lawful targets. This suggests two conclusions. Firstly, states may have wanted to guarantee themselves as much freedom as possible in fighting with non-state armed groups to quash a rebellion as fast as possible.Footnote ¹⁶⁵ In practice, states tend to refer to the opponent not as a party to the conflict, an armed group, or as combatants, choosing instead to call them bandits, terrorists, or criminals.Footnote ¹⁶⁶ This served to discourage the qualification of the situation as armed conflict and thus to prevent the application of IHL.

Secondly, the intention of the states was to limit the lawful options of attacking state targets. This is why the rights of combatants were not afforded to members of non-state armed groups, who in consequence have no clear right to participate in hostilities and no right to PoW status. Furthermore, the states decided against affording the status of combatants to members of their own armed forces, so as not to encourage potentially lawful attacks against them. The same reasons, in my view, stand behind the decision not to define a military objective in AP II. The idea was to prevent any provision of the law from suggesting encouragement to attack military personnel or public service officials, as well as, for example, military buildings and equipment.Footnote ¹⁶⁷ While IHL contains no prohibition for the non-state party to take part in hostilities, it allows the states to make it punishable under national law (Article 6(2) AP II).

In NIAC, the law always sides with the armed forces because they are an organ of the state, and the state shapes the law – and so, naturally, the law promotes the interests of the state.Footnote ¹⁶⁸ States have blocked the option of granting non-state armed groups the same rights and duties that states enjoy, even if the degree of organization of the non-state group, the designation of its members, and the implementation of IHL is comparable to a state’s armed forces.Footnote ¹⁶⁹ Granting rights to the non-state party is perceived as undue legitimization.Footnote ¹⁷⁰ Public opinion is apparently accepting of this imbalance and is even willing to accept violations of the few IHL norms that apply to NIAC by armed forces for the sake of effectiveness of operation.Footnote ¹⁷¹

However, in my opinion, at the heart of modern international law is not the state and its traditionally understood sovereignty; rather, the focus is on the human being and humanity as such.Footnote ¹⁷² Therefore, it should be considered if it would not be in the interest of humanity – and certainly its civilian population – to ensure equal treatment of all parties to the conflict, both in IAC and NIAC. When a group of people in a state rises against that state, and thus clearly feels that they are not represented by that state properly, why should that group of people be barred from enjoying equal treatment under international law when it comes to the rules of conduct of hostilities? The question is now asked more and more frequently: is the state-centric approach to creating IHL still legitimate,Footnote ¹⁷³ or should the armed groups which are expected to implement IHL be able to contribute to its creation?Footnote ¹⁷⁴

1.4.1 Definition of an Attack

When a person or object is classified as a lawful (potential) target, it might become subject to attack. To be clear, what is contemplated here is not accidental damage but rather deliberate and direct attack against this person or object, intended to kill/wound/capture the person or destroy/capture/neutralize the object.Footnote ¹⁷⁵

Article 49(1) AP I defines attacks as ‘acts of violence against the adversary, whether in offence or in defence’.Footnote ¹⁷⁶ While AP I only applies in IAC, the definition holds for NIAC too, as the letter of Article 13(2) AP II also refers to the notion of ‘acts of violence’.Footnote ¹⁷⁷ ICRC notes that from the very beginning of the diplomatic conference where both the additional protocols were negotiated, the states understood and agreed that the notion of an attack must be understood consistently regardless of the type of conflict.Footnote ¹⁷⁸

The definition emphasizes that the current situation of the party (i.e. whether it is engaging in offensive or defensive operations) is irrelevant; if the decision to use force is made against a specific person or object, this use of force is classified as an attack and consequently is subject to all restrictions as to the scope, methods, and means of warfare. The use of the plural in Article 49(1) AP I (‘attacks’) indicates that an operation is not assessed as a whole. Rather, restrictions apply to each element of each operation (in other words, to each shot fired, or to each instance of use of kinetic force towards a target). The restrictions apply to attacks from the ground, from the air, and from the sea (Article 49(3) AP I).

The APs use the phrase ‘acts of violence’, which prompts questions as to the types of permissible violence and the intended consequences of its use. If no violence is used, then the actions are not an attack under IHL, even if their consequences for the other party are dire (e.g. if money in the accounts of an armed group is confiscated, rendering the group unable to purchase arms necessary to continue participating in the hostilities). The purpose of IHL is to regulate hostilities rather than economic or ideological operations, and so, in my view, the term ‘violence’ as used in Article 49(1) AP I should be understood in principle as armed violence, or more precisely as physical violence (regardless of the use of any weapons). The intended consequence of the use of violence is understood as killing or wounding a person (be it a person with a protected status or not) or destroying or damaging objects.Footnote ¹⁷⁹ The principles of IHL apply whether the attack consists of a single shot fired by a sniper or massive shelling by artillery.Footnote ¹⁸⁰

Beside traditional hostilities conducted on land, on sea, and in the air, IHL is also relevant when assessing actions taken in cyberspace.Footnote ¹⁸¹ This is somewhat controversial in that cyberwarfare is conducted without the use of kinetic force. However, there is no doubt that the use of biological or chemical weapons, also not necessarily involving kinetic force, falls under IHL regulations. Cyberattacks targeting infrastructure (computer network attacks) can cause damage comparable to conventional attacks, for example destruction of servers or military equipment, and can, for instance, lead to changes in drug dosage, thus killing patients, giving control of weapons to attackers, etc. Sometimes, the scale of damage can even be comparable to weapons of mass destruction, such as interference with software that controls dams or nuclear power plants.Footnote ¹⁸²

Another argument that has gained traction recently is as follows: it is accepted that the consequence of an attack against a military objective is not necessarily, in so far as an object is concerned, its destruction; capture or neutralization are other possible outcomes. By the same token, cyberattacks need not necessarily lead to destruction, wounding, or killing to qualify as attacks under IHL. For instance, if feeding false data to a computer system (computer network exploitation) disables an entire defence system, this action is an attack under IHL. As a result, operations in cyberspace are increasingly viewed through the lens of Article 49(1) AP I, with all the consequences thereof – for example, the application of the principles of distinction and proportionality.Footnote ¹⁸³

1.4.2 Permissible Degree of Force

Article 49(1) AP I offers no specific indication of the degree of force that can be used when launching an attack against a person or object. This prompts the crucial question: does attacking under IHL mean that the tactic of shooting to kill is allowed, or is the only permissible tactic to first attempt to capture the person; if impossible – wound, and only if that proves impossible – kill? As regards objects, the dilemma would be: should total destruction be the objective from the start, or should an effort be made to preserve the object as much as possible, or at least to limit the damage? There are no definite answers to those questions as both sides in the dispute use convincing arguments.

In section IX, the ICRC Interpretive Guidance stipulates that ‘the kind and degree of force which is permissible against persons not entitled to protection against direct attack must not exceed what is actually necessary to accomplish a legitimate military purpose in the prevailing circumstances’.Footnote ¹⁸⁴ In line with this recommendation, when wounding a person is sufficient to put that person out of action, the person should be wounded and not killed. If capture is an option, the person should be captured rather than wounded or killed.Footnote ¹⁸⁵

The crucial issue was that nowhere in the GC and APs is it stipulated that the least harmful method of attack must be used.Footnote ¹⁸⁶ If a person is a lawful target under IHL, killing is allowed whether or not it was physically possible to capture or wound that person because, for instance, they were eating or sleeping at the moment of the attack.Footnote ¹⁸⁷ However, cold-blooded slaughter of a person who is a lawful target if the circumstances would have allowed for easy capture is difficult to reconcile with the principle of humanity.Footnote ¹⁸⁸ Furthermore, the need to seek the least harmful method may result from Article 35 AP I, which reads ‘the right of the Parties to the conflict to choose methods or means of warfare is not unlimited’.Footnote ¹⁸⁹ The wording focuses not only on the different kinds of weapons (means) but also on the way they are used (methods), including the degree of force to be used in an attack. This is a great development of constraints on the conduct of hostilities in comparison to Article 22 HR, for example, which referred only to the means of warfare.

Under Article 35 AP I it is prohibited to employ methods of warfare that cause ‘superfluous injury or unnecessary suffering’, which in my opinion also means – contrary to some voices in literature on the subjectFootnote ¹⁹⁰ – a prohibition of unnecessary deaths.Footnote ¹⁹¹ To use argumentum a minori ad maius, if no unnecessary injury and suffering is allowed, the same is also true with regard to unnecessary deaths.Footnote ¹⁹²

A permissible military purpose under IHL is to weaken the adversary; this does not necessarily mean killing the enemy’s soldiers.Footnote ¹⁹³ The same purpose may be accomplished by taking them prisoner or by wounding them and thus putting them out of action. However, it has been argued that wounding an enemy rarely actually eliminates the person from combat. Brutal as it sounds, studies have demonstrated that really only a hit to the brain or upper spinal cord eliminates the risk of a counterattack.Footnote ¹⁹⁴ Moreover, under specific circumstances killing a person may actually be more humane than wounding them.Footnote ¹⁹⁵

Jean Pictet argued that killing a combatant if capture was a viable option violates the principle of proportionality given that the only permissible objective is to weaken the adversary.Footnote ¹⁹⁶ However, the proponents of the shoot-to-kill tactic note that AP I contemplates the issue of proportionality solely in the context of civilian losses and not lawful targets.Footnote ¹⁹⁷ There is actually no consensus on that issue; certainly not everyone agrees that proportionality is irrelevant when it comes to lawful targets.Footnote ¹⁹⁸ Each IHL principle should be interpreted in light of its other principles. Whether or not the principles of proportionality, humanity, military necessity, prohibition of unnecessary suffering, etc., are directly invoked, the fact remains that murder without a clear need for it is not allowed. It would be paradoxical if the military necessity of attacking objects would have to be contemplated before the attack (Article 52(2) AP I requires an assessment of whether the destruction of the object will bring a definite military advantage), but no similar considerations are required when it comes to taking a person’s life.

It cannot be ignored that when conducting hostilities, the element of surprise may be of the utmost importance. As there is no prohibition in IHL of ruses of war (Article 37(2) AP I),Footnote ¹⁹⁹ a requirement to offer a chance to surrender in each case would be irreconcilable with surprise attacks. Thus, it can be argued that as long as the armed conflict continues, killing persons who are legitimate targets must remain lawful.Footnote ²⁰⁰

On the one hand, it is unreasonable to expect a soldier to consider in each situation which method is the most fitting, and to choose the approach that is least harmful to the enemy depending on the prevailing circumstances. To cite Frits Kalshoven’s analogy, a soldier is not a golfer on a golf course, free to deliberate which golf club to use for each strike.Footnote ²⁰¹ Quite the opposite: a soldier is expected to accomplish an objective as time- and resource-effectively as possible. Capture instead of killing is less effective in terms of money, time, duration for which the enemy is put out of action,Footnote ²⁰² and risk to soldiers on the same side of the conflict.Footnote ²⁰³ Thus, if enemy members of armed forces or of armed groups are captured rather than killed, the conflict may be prolonged and cause the overall death toll to rise.Footnote ²⁰⁴

On the other hand, while a soldier may not be expected to deliberate on the choice of means of each and every attack, such expectation stands to reason with regard to the command. For instance, while air strikes are generally permissible (even though they offer very little choice of capture or wounding the adversary’s soldiers), in certain specific circumstances they could be considered illegal due to their impact. The argument that effectiveness of operations depends on the speed of operations no longer holds true; many conflicts today are inherently long term. Often the official end of military operations is followed by a stabilization mission, which in theory involves no significant combat components but in practice tends to encompass a lot of fighting. Examples include the interventions in Iraq in 2003 and in Afghanistan after 2001. The conflicts drag on not due to the prevalence of capture instead of killing; in my opinion, quite the opposite is true: preference for capture over killing may paradoxically promote ultimate victory, because they help to ‘win the hearts and minds’ of the local population.

As regards attacks against objects, Article 52(2) sentence 2 AP I reads ‘In so far as objects are concerned, military objectives are limited to those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage.’ This wording clearly indicates that there are various ways in which an attack can be structured. An object that is a military objective may be destroyed, in which case the attack will render it useless for any of the parties. It may be captured – that is, physical control of it may be taken over – and thus the adversary will no longer be able to use it. Finally, it may be neutralized, meaning that the object will cease to be a military asset for the adversary, but will not be physically taken over.Footnote ²⁰⁵ The overall objective is to weaken rather than totally destroy the enemy – for example, if the enemy’s progress can be blocked using anti-tank mines, it is unnecessary to destroy the entire road network (used not only by the military personnel but also by civilians). Recent practice of states – such as the use of graphite bombs to temporarily disable electrical power systems – suggests that neutralization is becoming the tactic of choice in relation to objects that may easily become military objectives due to their possible future use or location.Footnote ²⁰⁶

Another argument in favour of using the least harmful degree of force is the need to take into account the norms of IHRL, which only allow physical force to be used if and when absolutely necessary.Footnote ²⁰⁷ It has been argued that this standard should only apply in NIAC (and not in IAC), because only in the context of NIAC is the issue of use of force against specific categories of persons and objects not explicitly regulated.Footnote ²⁰⁸ However, I think that a differentiation of standards of the use of force in IAC and NIAC is completely impracticable: the training of troops must be consistent regardless of the type of conflict.Footnote ²⁰⁹ Furthermore, while international courts have not so far questioned the legality of attacks against legitimate targets,Footnote ²¹⁰ national courts have in some cases enforced the standard of graduated use of force.Footnote ²¹¹ Interestingly, even the practices of states that have opposed the principle of graduated use of force against military objectives demonstrate a certain willingness on the part of these states to comply with this rule and thus limit the impact of the use of force to the extent to which it is possible.Footnote ²¹²

In my opinion, bearing in mind the specific provisions of IHL concerning limitations of not only the means but also of the methods of warfare, the understanding or interpretation in bona fide of general principles (i.e. principle of humanity and of military necessity which aim is to limit any kind of losses to the minimum necessary to accomplish military aims), and the impact of IHRL on the interpretation of IHL, the standard of using the lowest degree of force should be implemented in any kind of an armed conflict if circumstances are allowing for this. Importantly, the application of this standard is not equivocal to the obligation to take on an additional risk to the troops on the part of the party launching the attack.Footnote ²¹³

1.4.3 Restrictions on the Means and Methods of Warfare Used against Legitimate Targets

Beyond addressing the issue of the permissible degree of force to be used against lawful targets, IHL is also explicit as regards specific means and methods of warfare in this context. It is prohibited to kill, injure, or capture an adversary by dishonestly leading him ‘to believe that he is entitled to, or is obliged to accord, protection under the rules of international law applicable in armed conflict’ (Article 37(1) AP I).

AP I specifies that perfidy can take the following forms: the feigning of an intent to negotiate under a flag of truce or of a surrender; the feigning of an incapacitation by wounds or sickness; the feigning of civilian, non-combatant status; and the feigning of protected status by the use of signs, emblems, or uniforms of the United Nations or of neutral or other states not parties to the conflict.

Ruses of war are not prohibited under IHL. The difference between ruses and perfidy is that the former may mislead the adversary and encourage the abandonment of caution, but it is accomplished without a breach of confidence related to the status of a person or object. It is therefore perfectly legal (and explicitly listed as such in Article 37(2) AP I) to use camouflage, decoys, mock operations, and misinformation. If a person sneaks into a camp at night, wearing garments that are not suggestive of having a protected status, and kills a sleeping soldier with a knife, this is completely acceptable under IHL,Footnote ²¹⁴ as is, for example, hiding in a bush and launching a surprise attack. In cyberspace, it is considered impermissible, for instance, to report that hostilities have ended when in fact hostilities are still underway.Footnote ²¹⁵ Interestingly, because IHL prohibits methods of warfare that cause superfluous injury or unnecessary suffering (both physical and psychological), the argument has even been made that using a computer virus to disrupt communication may be illegal under its regulations.Footnote ²¹⁶

Whether a specific type of weapon indisputably qualifies as causing superfluous injury or unnecessary suffering is determined (only with regard to states parties) by an explicit treaty prohibition,Footnote ²¹⁷ as is the case, for example, with regard to small-calibre explosive projectiles,Footnote ²¹⁸ bullets which expand or flatten easily in the body,Footnote ²¹⁹ poison or poisoned weapons,Footnote ²²⁰ naval mines and torpedoes,Footnote ²²¹ anti-personnel mines and booby-traps,Footnote ²²² chemical weapons,Footnote ²²³ biological weapons,Footnote ²²⁴ weapons that cause environmental modification,Footnote ²²⁵ weapons that leave fragments not detectable in the human body by X-rays,Footnote ²²⁶ incendiary weapons,Footnote ²²⁷ blinding laser weapons,Footnote ²²⁸ weapons that leave explosive remnants,Footnote ²²⁹ and cluster munitions.Footnote ²³⁰ It is worth noting that there is no obligation to use only the most precise weapon available to a party.Footnote ²³¹