¹ For a call for states to do so, see Schmitt, Michael N and Watts, Sean, ‘The Decline of International Humanitarian Law Opinio Juris and the Law of Cyber Warfare’ (forthcoming 2014) 50Texas International Law JournalGoogle Scholar.

² As an example, NATO's September 2014 Wales Summit Declaration stated: ‘Our policy also recognises that international law, including international humanitarian law and the UN Charter, applies in cyberspace’: NATO, Wales Summit Declaration: Issued by the Heads of State and Government Participating in the Meeting of the North Atlantic Council in Wales, 5 September 2014, http://www.nato.int/cps/en/natohq/official_texts_112964.htm.

³ With regard to the conflict see Tikk, Eneken, Kaska, Kadri and Vihul, Liis, International Cyber Incidents: Legal Considerations (Cooperative Cyber Defence Centre of Excellence 2010) 66–90.Google Scholar The international legal community began to look at the subject in the late 1990s, the first major conference being held at the United States Naval War College in 1999, the proceedings of which were published as Schmitt, Michael N and O'Donnell, Brian T (eds), Computer Network Attack and International Law, International Law Studies, vol 78 (US Naval War College 2002)Google Scholar. However, following the events of 9/11, its attention was redirected towards issues surrounding counter-terrorism operations and the conflicts in Iraq and Afghanistan.

⁴ Schmitt, Michael N (ed), Tallinn Manual on the International Law Applicable to Cyber Warfare (Cambridge University Press 2013)Google Scholar (Tallinn Manual).

⁵ See, eg, NATO (n 2); Group of Governmental Experts on Developments in the Field of Information and Telecommunications in the Context of International Security, June 2013, UN Doc A/68/98, 24 para 19; Harold H Koh, ‘International Law in Cyberspace’, Address at the USCYBERCOM Inter-Agency Legal Conference, Ft Meade, Maryland, 18 September 2012, reprinted in (2012) 54 Harvard International Law Journal Online 1, 3–5; Advisory Council on International Affairs (the Netherlands), ‘Government [of the Netherlands] Response to the AIV/CAVV Report on Cyber Warfare’, http://www.aiv-advies.nl/ContentSuite/template/aiv/adv/collection_single.asp?id=1942&adv_id=3016&page=regeringsreacties&language=UK; ICRC, ‘International Humanitarian Law and the Challenges of Contemporary Armed Conflicts’, October 2011, Doc 31IC/11/5.1.2, 36–38.

⁶ Tallinn Manual (n 4) r 20; In particular, they pointed to Additional Protocol I, art 36, which requires legal review of new means and methods of warfare: Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (entered into force 7 December 1978) 1125 UNTS 3 (Additional Protocol I or AP I). Logically, the obligation could exist only if such means and methods were subject to existing IHL principles and rules.

⁷ For example, the US position on the equivalency of a ‘use of force’ and ‘armed attack’ under the jus ad bellum is reflected in the Manual, despite the fact that no members of the IGE agreed with it: Tallinn Manual (n 4) 47. For a recent confirmation of this position by the then Legal Adviser to the State Department, see Koh (n 5) 7.

⁸ Data is information in electronic form. The Tallinn Manual explains that it consists of ‘the basic elements that can be processed or produced by a computer’: Tallinn Manual (n 4) 258.

⁹ The ICRC has completed a monumental three-volume study on the subject: Henckaerts, Jean-Marie and Doswald-Beck, Louise (eds), Customary International Humanitarian Law, Vol I: Rules (ICRC and Cambridge University Press 2005, revised 2009)Google Scholar (ICRC Study). Concerns of the US regarding the study were set out in Bellinger, John B and Haynes, William J, ‘A US Government Response to the International Committee of the Red Cross's Customary International Humanitarian Law Study’ (2007) 89 International Review of the Red Cross 443Google Scholar. On the study, see also Breau, Susan and Wilmshurst, Elizabeth (eds), Perspectives on the ICRC Study on Customary International Humanitarian Law (Cambridge University Press 2007Google Scholar.

¹⁰ AP I (n 6) art 48, operationalised as to persons and objects in arts 51 and 52 respectively. The corresponding Tallinn Manual (n 4) rule is 31. See also ICRC (n 9) rr 1 and 7; Department of the Navy & Department of Homeland Security, ‘The Commander's Handbook on the Law of Naval Operations’, NWP 1-14M/MCWP 5-12/COMDTPUB P5800.7A, 2007 (NWP 1-14M), para 5.3.2.

¹¹ AP I (n 6) arts 51(5)(b), 57(2)(a)(iii), 57(2)(b). The corresponding Tallinn Manual (n 4) rule is 51. See also ICRC (n 9) rr 14, 18–19; NWP 1-14M (n 10) para 5.3.3.

¹² AP I (n 6) art 57. The corresponding Tallinn Manual (n 4) rules are 52–58. See also ICRC Study (n 9) rr 15–20; NWP 1-14M (n 10) para 8–1. On proportionality and precautions in cyber attacks, see Jensen, Eric Talbot, ‘Cyber Attacks: Proportionality and Precautions in Attack’ (2013) 89 International Law Studies 198Google Scholar.

¹³ To illustrate, I have highlighted in the footnotes the relevant rules of the ICRC Study (n 9) and, as an example of acquiescence by a non-party state, paragraphs from the most recent US military manual, NWP 1-14M (n 10), when first encountered.

¹⁴ Schmitt, Michael N, ‘The Law of Cyber Warfare: Quo Vadis?’ (2014) 25 Stanford Law and Policy Review 269Google Scholar; Schmitt, Michael N, ‘Rewired Warfare: Rethinking the Law of Cyber Attack’ (forthcoming 2014) 96 International Review of the Red CrossCrossRefGoogle Scholar.

¹⁵ The paradigmatic example being the well-known exchange on the issue of civilian direct participation in hostilities found in the New York University Journal of International Law and Politics by individuals who participated in the project leading to publication of the ICRC's interpretive guidance on the subject: Melzer, Nils (ed), Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law (ICRC 2009)Google Scholar; Watkin, Kenneth, ‘Opportunity Lost: Organized Armed Groups and the ICRC “Direct Participation in Hostilities” Interpretive Guidance’ (2010) 42 New York University Journal of International Law and Politics 641Google Scholar; Schmitt, Michael N, ‘Deconstructing Direct Participation in Hostilities: The Constitutive Elements’ (2010) 42 New York University Journal of International Law and Politics 697Google Scholar; Boothby, Bill, ‘“And For Such Time As”: The Time Dimension to Direct Participation in Hostilities’ (2010) 42 New York University Journal of International Law and Politics 741Google Scholar; Parks, W Hays, ‘Part IX of the ICRC “Direct Participation in Hostilities” Study: No Mandate, No Expertise, and Legally Incorrect’ (2010) 42 New York University Journal of International Law and Politics 769Google Scholar; Melzer, Nils, ‘Keeping the Balance between Military Necessity and Humanity: A Response to Four Critiques of the ICRC's Interpretive Guidance on the Notion of Direct Participation in Hostilities’ (2010) 42 New York University Journal of International Law and Politics 831Google Scholar.

¹⁶ Tallinn Manual (n 4) 124.

¹⁷ See also ICRC Study (n 9) r 7; NWP 1-14M (n 10) paras 5.3.2, 8.1 and 8.2.

¹⁸ Sandoz, Yves, Swinarski, Christophe and Zimmermann, Bruno (eds), Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 (ICRC 1987) (ICRC Commentary), para 2014Google Scholar.

¹⁹ Tallinn Manual (n 4) 125. On military objectives, see Jachec-Neale, Agnieszka, The Concept of Military Objectives in International Law and Targeting Practice (Routledge forthcoming 2015)Google Scholar.

²⁰ Tallinn Manual (n 4) 125. See also ICRC Study (n 9) r 8; NWP 1-14M (n 10) para 8.2.

²¹ Emphasis added.

²² Tallinn Manual (n 4) 127.

²³ Vienna Convention on the Law of Treaties (entered into force 27 January 1980) 1155 UNTS 331 (VCLT), art 31(1).

²⁴ ICRC Commentary (n 18) para 2008.

²⁵ Tallinn Manual (n 4) 106 r 30.

²⁶ ibid 107–08.

²⁷ ibid 108–09.

²⁸ ibid 126. Mr Mačák discusses ‘locations’ in his article, but no member of the IGE disputed the interpretation by which a location was encompassed in the meaning of the term ‘object’ since, after all, that is the plain meaning of the art 52(2) text. Note that locations are visible and tangible, the classic example being a mountain pass through which enemy forces intend to pass. On qualification of cyber targets by location, see Tallinn Manual (n 4) 128.

²⁹ ICRC Commentary (n 18) para 2017.

³⁰ Tallinn Manual (n 4) 127. Professor Marco Sassòli has observed that ‘[o]nly a material, tangible thing can be a target’: Marco Sassòli, ‘Legitimate Targets of Attacks under International Humanitarian Law’ (2003) International Humanitarian Law Research Initiative Working Paper, January 2003, 2.

³¹ The Tallinn Manual clearly explains its use of citation in the introduction, an explanation that in part accounts for the sole citation: Tallinn Manual (n 4) 7–9.

³² VCLT (n 23) art 31(1). On art 31, see Sorel, Jean-Marc and Bore-Eveno, Valerie, ‘Article 31’ in Corten, Olivier and Klein, Pierre (eds), The Vienna Conventions on the Law of Treaties: A Commentary (Oxford University Press 2011) 804Google Scholar. As they note, ‘[i]t is thus fairly obvious that the text of Article 31 is a true example of a compromise: a compromise between the defenders of textual interpretation, of subjective interpretation based on the parties’ intention, and of end-focused or teleological interpretation which attempts to extract those meanings from the text which might be intended beyond the formulation used': ibid 808. See also Jonas, David S and Saunders, Thomas N, ‘The Object and Purpose of a Treaty: Three Interpretive Methods’ (2010) 43 Vanderbilt Journal of Transnational Law 565Google Scholar, 577–81. Moreover, with respect to the IGE's citation of only art 31(1), the remaining paragraphs of the article serve primarily to supplement and expound on the first.

³³ Vienna Convention (n 22) art 32(a). On art 32, see Yves le Bouthillier, ‘Article 32’ in Corten, Olivier and Klein, Pierre (eds), The Vienna Conventions on the Law of Treaties: A Commentary (Oxford University Press 2011) 841Google Scholar.

³⁴ AP I (n 6) art 36. See also NWP 1-14M (n 10) para 5.3.4 (albeit limited to reviews of weapons). The IGE agreed that the reference to ‘means’ in the article was customary in nature, but did not agree on the character of the requirement to review methods of warfare: Tallinn Manual (n 4) 153–54.

³⁵ Tallinn Manual (n 4) 5.

³⁶ Fitzmaurice, Gerald, ‘The Law and Procedure of the International Court of Justice 1951–54: Treaty Interpretation and Other Treaty Points’ (1957) 33 British Year Book of International Law 203Google Scholar, 212.

³⁷ On the issue, see Schmitt, Michael N, ‘Military Necessity and Humanity in International Humanitarian Law: Preserving the Delicate Balance’ (2010) 50 Virginia Journal of International Law 795Google Scholar.

³⁸ For instance, all new weapons are subject to the rule that they must be discriminate, but advances in precision have rendered the international community's understanding of what it means to be discriminate more demanding: see generally, Markham, Christopher and Schmitt, Michael N, ‘Precision Air Warfare and the Law of Armed Conflict’ (2013) 89 International Law Studies 669Google Scholar.

³⁹ Tallinn Manual (n 4) r 32.

⁴⁰ The International Criminal Tribunal for the former Yugoslavia, in a well-accepted characterisation, has described non-international armed conflict as ‘protracted armed violence between governmental authorities and organized armed groups or between such groups within a State’: ICTY, Prosecutor v Tadić, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, IT-94-1-AR72, Appeals Chamber, 2 October 1995, [70]. On the question of organised armed groups in the cyber context see Tallinn Manual (n 4) 88–90. See also Schmitt, Michael N, ‘Classification of Cyber Conflict’ (2013) 89 International Law Studies 233, 245–48Google Scholar.

⁴¹ On the targetability of members of an organised armed group, see Melzer (n 15) 70–73 (regarding the temporal scope of protection). Some controversy exists surrounding the ICRC's assertion that to qualify as a member of an organised armed group, the individual concerned must have a ‘continuous combat function’ therein: Tallinn Manual (n 4) 116–17. For my views on the subject, see Schmitt, Michael N, ‘The Interpretive Guidance on the Notion of Direct Participation in Hostilities: A Critical Analysis’ (2010) 1 Harvard National Security Journal 5, 21–24Google Scholar.

⁴² Tallinn Manual (n 4) 89.

⁴³ ibid 89.

⁴⁴ ibid 89–90.

⁴⁵ See discussion in Tallinn Manual (n 4) 88: ‘… a group is armed if it has the capacity of undertaking cyber attacks’ (r 30)); Schmitt (n 40) 248–49.

⁴⁶ See discussion in Tallinn Manual (n 4) 88; Schmitt (n 40) 248–49.

⁴⁷ Tallinn Manual (n 4) 160. For an identical conclusion beyond the context of cyber operations, see HPCR Manual on International Law Applicable to Air and Missile Warfare (Cambridge University Press 2013) commentary accompanying r 14Google Scholar.

⁴⁸ Statement of US Representative, ‘Official Records of the Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts’, Geneva, 7 February 1975, CDDH/III/SR.15, vol XIV, 119. Professor Yoram Dinstein has noted that ‘[t]he noun “objects”, used in the definition, clearly encompasses material and tangible things. However, the phrase “military objectives” is certainly not limited to inanimate objects, and it is wrong to suggest that the Protocol's language fails to cover enemy military personnel. To be on the safe side, the framers of Article 52(2) added the (otherwise superfluous) words “[i]n so far as objects are concerned,” underscoring that not only inanimate objects constitute military objectives. Human beings can categorically come within the ambit of military objectives. Indeed, human beings are not the only living creatures that do. Certain types of animals – cavalry horses and pack mules in particular – can also be legitimate targets’: Dinstein, Yoram, ‘Legitimate Military Objectives under the Current Jus in Bello’ (2002) 78 International Law Studies 140, 142–43Google Scholar. Thus, he views objects as material, tangible and inanimate, but accepts, as did the IGE, that humans can also qualify as military objectives, albeit by different criteria. See also Dinstein, Yoram, The Conduct of Hostilities in International Armed Conflict (2nd edn, Cambridge University Press 2010) 92Google Scholar (‘Since the noun “objects” intrinsically relates to material and tangible things, the definition must be regarded as confined to inanimate objects’).

⁴⁹ Report of the International Law Commission on the Work of the Second Part of Its Seventh Session (1966) 2 Yearbook of the International Law Commission 169Google Scholar, 220, UN Doc A/6309/Rev 1 (‘the text must be presumed to be the authentic expression of the intentions of the parties’ and ‘the starting point of interpretation is the elucidation of the meaning of the text, not an investigation ab initio into the intentions of the parties’).

⁵⁰ Psychological operations are especially useful in counter-insurgency, stability and counter-terrorism operations. According to NATO, ‘in complex political and social contexts where the will of the indigenous population becomes the metaphorical vital ground (i.e. it must be retained or controlled for success), there is a requirement to influence and shape perceptions through the judicious fusion of both physical and psychological means’: NATO, ‘Allied Joint Doctrine’, December 2010, AJP-01 (D), 2–10. See also, generally, NATO, ‘Allied Joint Doctrine for Civil-Military Cooperation’, February 2013, AJP-3.4.9; NATO, ‘Allied Joint Doctrine for Psychological Operations’, October 2007, AJP-3.10.1(A). It should be cautioned that psychological operations, despite their generally negative image, may have such humanitarian purposes as exhorting the population to refrain from participating in war crimes, crimes against humanity or genocide; allow the unimpeded transit of humanitarian assistance; respect the work of non-governmental organisations; provide objective news; and warn the civilian population to stay away from areas where combat is likely to occur.

⁵¹ AP I (n 6) art 52(2).

⁵² Tallinn Manual (n 4) 108.

⁵³ HCJ 769/02, Public Committee Against Torture in Israel and Palestinian Society for the Protection of Human Rights and the Environment v Israel and Others ILDC 597 (IL 2006) [2006], para 28.

⁵⁴ ICRC Commentary (n 18) paras 2007–08 (emphasis added).

⁵⁵ AP I (n 6) art 52(2); Tallinn Manual (n 4) r 38.

⁵⁶ AP I (n 6) art 49; Tallinn Manual (n 4) r 30: the Manual does not address this issue head on because of the majority view that data does not qualify as an object.

⁵⁷ AP I (n 6) art 52(2).

⁵⁸ For a general discussion of the process of contemporary targeting from a legal perspective, see Schmitt, Michael N and Widmar, Eric, ‘“On Target”: Precision and Balance in the Contemporary Law of Targeting’ (forthcoming 2014) 7 Journal of National Security Law and PolicyGoogle Scholar. See also Boothby, William H, The Law of Targeting (Oxford University Press 2012)Google Scholar; Henderson, Ian, The Contemporary Law of Targeting: Military Objectives, Proportionality and Precautions in Attack under Additional Protocol I (Brill 2009)CrossRefGoogle Scholar. On targeting practices generally, see US Chairman of the Joint Chiefs of Staff, ‘Joint Publication 3-60, Joint Targeting’, 31 January 2013.

⁵⁹ He cites Schmitt, Michael N, ‘Cyber Operations and the Jus in Bello: Key Issues’ (2011) 87 International Law Studies 89Google Scholar, 92–96; Schmitt, ‘Quo Vadis’ (n 14) 298.

⁶⁰ Tallinn Manual (n 4) 106, 112.

⁶¹ See, eg, AP I (n 6) arts 51, 52, 54–58. For my views on this issue, see Schmitt, ‘Rewired Warfare’ (n 14); Schmitt, Michael N, ‘“Attack” as a Term of Art in International Law: The Cyber Operations Context’ in Czosseck, Christian, Ottis, Rain and Ziolkowski, Katharina (eds), Proceedings of the 4th International Conference on Cyber Conflict (Cooperative Cyber Defence Centre of Excellence 2012) 283Google Scholar, 289–93. See also Droege, Cordula, ‘Get Off My Cloud: Cyber Warfare, International Humanitarian Law, and the Protection of Civilians’ (2012) 94 International Review of the Red Cross 533Google Scholar, 556–60; ICRC (n 5) 37–38.

⁶² See also ICRC Study (n 9) 4.

⁶³ Tallinn Manual (n 4) 106–107.

⁶⁴ ibid r 30.

⁶⁵ ibid 108–09.

⁶⁶ Schmitt, ‘Cyber Operations and the Jus in Bello’ (n 59) 91.

⁶⁷ ibid 96.

⁶⁸ Professor Noam Lubell, cited by Mr Mačák, has been careful to make the distinction between the issues of object and attack. Although he arrives at a different result from mine, his methodological approach is valid: Lubell, Noam, ‘Lawful Targets in Cyber Operations? Does the Principle of Distinction Apply?’ (2013) 89 International Law Studies 252, 261–64Google Scholar.

⁶⁹ Tallinn Manual (n 4) 107–08.

⁷⁰ ibid 109.

⁷¹ ibid r 71.

⁷² He argues that the object and purpose of AP I carries an additional degree of relevance for those states that have signed but not ratified this instrument – a category which includes, but is not limited to, the United States, citing art 18 of the Vienna Convention on the Law of Treaties. States in this position must refrain from acts that would undermine the object and purpose of the treaty. This ignores the fact that the US has, over decades, ‘made its intention clear not to become a party to the treaty’ and therefore is relieved of this obligation: VCLT (n 23) art 18(a). See, eg, President Ronald Reagan, ‘Message to the Senate Transmitting a Protocol to the 1949 Geneva Conventions’, 29 January 1987, http://www.reagan.utexas.edu/archives/speeches/1987/012987b.htm.

⁷³ Schmitt (n 37) 798–99.

⁷⁴ Hague Convention (IV) respecting the Laws and Customs of War on Land and its annex: Regulation concerning the Laws and Customs of War on Land, Martens Nouveau Recueil (ser 3) 461 (entered into force 26 January 1910), art 22; Hague Convention (II) Convention with Respect to the Laws and Customs of War on Land and its annex: Regulations concerning the Laws and Customs of War on Land, 26 Martens Nouveau Recueil (ser 2) 949 (entered into force 4 September 1900) art 22. The principle also appears in AP I, albeit with the addition of ‘methods’ of warfare: AP I (n 6) art 35(1). Methods generally refer to tactics, whereas means refer to weapons.

⁷⁵ United States v List (The Hostages Case), Case No. 7 (19 February 1948), reprinted in Trials of War Criminals before the Nuremberg Military Tribunals under Control Council Law No. 10, Vol xi (1950) 1230, 1253–56.

⁷⁶ AP I (n 6) arts 51(5)(b), 57(2)(a)(iii), 57(2)(b).

⁷⁷ On spear phishing, see ‘Spear Phishing: Scam, Not Sport’, Norton, http://us.norton.com/spear-phishing-scam-not-sport/article. On watering-hole attacks, see ‘Watering Hole Attacks’, Symantec, https://www.symantec.com/content/en/us/about/media/pdfs/b-istr_18_watering_hole_edits.en-us.pdf.

⁷⁸ ‘Trends 2014: Beyond the Breach’, Mandiant, 4–7, http://connect.mandiant.com/m-trends_2014.

⁷⁹ Tallinn Manual (n 4) 130.

⁸⁰ ibid 108.

⁸¹ ibid 109.

⁸² The issue of targeting civilians, civilian objects and other persons and objects arose during the deliberation over the ICRC's Interpretive Guidance. All of the experts agreed that a person who inflicts death, injury or destruction on persons or objects could qualify as a direct participant and, assuming the other two constitutive elements were met, be targeted; thus, by definition, they were a military objective: Melzer (n 15) 49–50.

⁸³ ICRC, ‘Conference of Government Experts on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts: Report on the Work of the Conference’, Geneva, Second Session, 3 May–3 June 1972, Vol I, July 1972, para 3.128.

⁸⁴ ICRC Study (n 9) 32.

⁸⁵ Although Dr Harrison Dinniss fails to acknowledge the fact, the IGE was actually split on whether physical damage or injury is a criterion for ‘attacks’. The majority view was that such consequences were, in the present state of the law, required, but extended the notion of damage to certain interference with functionality: Tallinn Manual (n 4) 108–09.

⁸⁶ The IGE was actually making a different point, one that dealt with the issue of whether an act involved ‘violence’ such that it could qualify as an ‘attack’. It was not addressing the tangibility of the weapon: Tallinn Manual (n 4) 106 (‘“Acts of violence” should not be understood as limited to activities that release kinetic force. This is well settled in the law of armed conflict. In this regard, note that chemical, biological, or radiological attacks do not usually have a kinetic effect on their designated target, but it is universally agreed that they constitute attacks as a matter of law’).

⁸⁷ On cyber weapons, see Boothby, William H, ‘Methods and Means of Cyber Warfare’ (2013) 89 International Law Studies 387Google Scholar.

⁸⁸ Tallinn Manual (n 4) 229–30.

⁸⁹ ibid rr 71, 74, 76, 79, 82, 84–86.

⁹⁰ ibid rr 80–81, 83.

⁹¹ ibid 205.

⁹² ibid r 71.

⁹³ ibid 206.

⁹⁴ ibid 241.

⁹⁵ Tallinn Manual (n 4) 159.

⁹⁶ For instance, I have rethought my formerly rigid understanding of the term ‘attack’ over the past decade based on discussions that occurred during the Tallinn Manual process and elsewhere, as well as interaction with state legal advisers on the matter: Schmitt, ‘Rewired Warfare’ (n 14).

⁹⁷ Schmitt, ‘Quo Vadis’ (n 14) 297.

⁹⁸ For a thoughtful article on the issue, see Geiß, Robin and Lahmann, Henning, ‘Cyber Warfare: Applying the Principle of Distinction in an Interconnected Space’ (2012) 45(3) Israel Law Review 381Google Scholar.