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Wired warfare 3.0: Protecting the civilian population during cyber operations

Published online by Cambridge University Press:  27 May 2019

Michael N. Schmitt
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Abstract

As a general matter, international humanitarian law is up to the task of providing the legal framework for cyber operations during an armed conflict. However, two debates persist in this regard, the resolution of which will determine the precise degree of protection the civilian population will enjoy during cyber operations. The first revolves around the meaning of the term “attack” in various conduct of hostilities rules, while the second addresses the issue of whether data may be considered an object such that operations destroying or altering it are subject to the prohibition on attacking civilian objects and that their effects need be considered when considering proportionality and the taking of precautions in attack. Even if these debates were to be resolved, the civilian population would still face risks from the unique capabilities of cyber operations. This article proposes two policies that parties to a conflict should consider adopting in order to ameliorate such risks. They are both based on the premise that military operations must reflect a balance between military concerns and the interest of States in prevailing in the conflict.

Keywords

cyber operationsattacksdatacivilian objectsproportionalityprecautions in attackmilitary necessity
Type
Selected articles
Information
International Review of the Red Cross , Volume 101 , Issue 910: Memory and war , April 2019 , pp. 333 - 355
Copyright
Copyright © icrc 2019 

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Footnotes

*

The views expressed in this article are those of the author in his personal capacity. The author is grateful to Lieutenant-Colonel Jeffrey Biller (USAF) for his invaluable comments.

References

1 Michael N. Schmitt and Liis Vihul, “International Cyber Law Politicized: The UN GGE's Failure to Advance Cyber Norms”, Just Security, 30 June 2017, available at: www.justsecurity.org/42768/international-cyber-law-politicized-gges-failure-advance-cyber-norms/.

2 UN GGE, Report of the Group of Governmental Experts on Developments in the Field of Information and Telecommunications in the Context of International Security, UN Doc. A/70/174, 22 July 2015, para. 28(d).

3 Brian J. Egan, Legal Adviser, US Department of State, “Remarks on International Law and Stability in Cyberspace”, 10 November 2016, available at: https://perma.cc/B6TH-232L. See also “Applicability of International Law to Conflicts in Cyberspace”, Digest of United States Practice in International Law, 2014, Chap. 18, section A(3)(b), p. 737; Harold Koh, Legal Adviser, US Department of State, “International Law in Cyberspace”, Remarks at the US Cyber Command Inter-Agency Legal Conference, 18 September 2012. On the Koh statement, see Schmitt, Michael N., “International Law in Cyberspace: The Koh Speech and Tallinn Manual Juxtaposed”, Harvard Journal of International Law Online, Vol. 54, 2012Google Scholar.

4 North Atlantic Council, Wales Summit Declaration, 5 September 2014, para. 72, available at : www.nato.int/cps/ic/natohq/official_texts_112964.htm. See also European Commission, Cybersecurity Strategy of the European Union: An Open, Safe and Secure Cyberspace, 7 February 2013, p. 72.

5 ICRC, “Cyberwarfare and International Humanitarian Law: The ICRC's Position”, June 2013, p. 2, available at: www.icrc.org/eng/assets/files/2013/130621-cyberwarfare-q-and-a-eng.pdf.

6 See, e.g., Schmitt, Michael N. (ed.), Tallinn Manual on the International Law Applicable to Cyber Warfare, Cambridge University Press, Cambridge, 2013CrossRefGoogle Scholar, Rule 20; Schmitt, Michael N. (ed.), Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations, Cambridge University Press, Cambridge, 2017CrossRefGoogle Scholar (Tallinn Manual 2.0), Rule 80.

7 Boothby, William H., Weapons and the Law of Armed Conflict, Oxford University Press, Oxford, 2009, pp. 340–341CrossRefGoogle Scholar; ICRC, A Guide to the Legal Review of New Weapons, Means and Methods of Warfare, January 2006, pp. 3–4.

8 International Court of Justice (ICJ), Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 8 July 1996, ICJ Reports 1996, paras 85–86.

9 Protocol Additional (I) to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts, 1125 UNTS 3, 8 June 1977 (AP I), Art. 36.

10 Office of the General Counsel, US Department of Defense, Law of War Manual, revised ed., December 2016 (US Law of War Manual), para. 16.6; US Air Force, Legal Review of Weapons and Cyber Capabilities, AF Instruction 51-402, 27 July 2011.

11 For an excellent comprehensive survey of the IHL issues arising from cyber operations, see Cordula Droege, “Get Off My Cloud: Cyber Warfare, International Humanitarian Law, and the Protection of Civilians”, International Review of the Red Cross, Vol. 94, No. 886, 2012.

12 AP I, Art. 51(2); Jean-Marie Henckaerts and Louise Doswald-Beck (eds), Customary International Humanitarian Law, Vol. 1: Rules, Cambridge University Press, Cambridge, 2005 (ICRC Customary Law Study), Rule 1; Protocol Additional (II) to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-international Armed Conflicts, 1125 UNTS 609, 8 June 1977 (AP II), Art. 4(i). See also Tallinn Manual 2.0, above note 6, Rule 94.

13 See, e.g., Rome Statute of the International Criminal Court, 2187 UNTS 90, 17 July 1998 (Rome Statute), Arts 8(2)(b)(i), 8(2)(c)(i).

14 AP I, Arts 51(5)(b), 57(2)(a)(iii), 57(2)(b); ICRC Customary Law Study, above note 12, Rule 14; Tallinn Manual 2.0, above note 6, Rule 113.

15 AP I, Art. 57; ICRC Customary Law Study, above note 12, Chap. 5; Tallinn Manual 2.0, above note 6, Rules 114–120. See also Jensen, Eric, “Cyber Attacks: Proportionality and Precautions in Attack”, International Law Studies, Vol. 89, 2012Google Scholar.

16 See generally AP I, Part IV, section I. Some scholars would extend application of the rules beyond attacks despite the use of the term in the rules themselves. See, e.g., Nils Melzer, Cyberwarfare and International Law, UNIDIR Resources Paper, 2011, p. 27, available at: http://unidir.org/files/publications/pdfs/cyberwarfare-and-international-law-382.pdf (arguing that applicability depends on whether the cyber operations constitute “hostilities”); Heather Harrison Dinniss, Cyber Warfare and the Laws of War, Cambridge University Press, Cambridge, 2012, pp. 196–202 (focusing on the reference to “military operations” in Article 48 of AP I).

17 AP I, Art. 52(1); ICRC Customary Law Study, above note 12, Rule 7; Tallinn Manual 2.0, above note 6, Rule 99.

18 Schmitt, Michael N., “Wired Warfare: Computer Network Attack and Jus in Bello”, International Review of the Red Cross, Vol. 84, No. 846, 2002Google Scholar; Schmitt, Michael N., “Rewired Warfare: Rethinking the Law of Cyber Attack”, International Review of the Red Cross, Vol. 96, No. 893, 2014CrossRefGoogle Scholar. See also Dörmann, Knut, “Applicability of the Additional Protocol to Computer Network Attack”, in Bystrom, Karin (ed.), Proceedings of the International Expert Conference on Computer Network Attacks and the Applicability of International Humanitarian Law, Stockholm, 17–19 November 2004, Swedish National Defence College, 2005Google Scholar, available at: www.icrc.org/eng/resources/documents/misc/68lg92.htm. See also Michael N. Schmitt, “‘Attack’ as a Term of Art in International Law: The Cyber Operations Context”, in Christian Czosseck, Rain Ottis and Katharina Ziolkowski (eds), Proceedings of the 4th International Conference on Cyber Conflict, NATO Cooperative Cyber Defence Centre of Excellence, 2012.

19 Pictet, Jean, Development and Principles of International Humanitarian Law, Martinus Nijhoff, Dordrecht and Boston, MA, 1985, pp. 61–63Google Scholar. On my approach to this balancing, see Schmitt, Michael N., “Military Necessity and Humanity in International Humanitarian Law: Preserving the Delicate Balance”, Virginia Journal of International Law, Vol. 50, No. 4, 2010Google Scholar.

20 An attack in the context of IHL is not to be confused with the jus ad bellum term “armed attack” found in Article 51 of the UN Charter. The analysis set forth in this article is limited to the former.

21 AP I, Arts 51(2), 52(1). On their customary status, see ICRC Customary Law Study, above note 12, Rules 1, 7.

22 AP I, Art. 51(4); ICRC Customary Law Study, above note 12, Rule 11.

23 AP I, Art. 37(1); ICRC Customary Law Study, above note 12, Rule 65. On the use of the term with respect to misuse of enemy emblems of nationality, see AP I, Art. 39(2); ICRC Customary Law Study, above note 12, Rule 62.

24 AP I, above note 9, Art. 12(1); ICRC Customary Law Study, above note 12, Rule 28. On the use of the term with respect to attacking medical aircraft, see AP I, Arts 27(2), 31(2).

25 AP I, Art. 54(2); ICRC Customary Law Study, above note 12, Rule 54.

26 AP I, Art. 55(2). The customary status of this rule is unsettled.

27 AP I, Art. 56(1). The customary status of this rule is unsettled.

28 AP I, Art. 59(1); ICRC Customary Law Study, above note 12, Rule 37.

29 AP I, Art. 41(1); ICRC Customary Law Study, above note 12, Rule 47. On the prohibition against attacking persons parachuting from aircraft in distress, see AP I, Art. 42.

30 AP I, Arts 51(5)(b), 57(2)(a)(iii), 57(2)(b); ICRC Customary Law Study, above note 12, Rules 14, 19.

31 AP I, Art. 57; ICRC Customary Law Study, above note 12, Rule 15.

32 For an excellent summary regarding the issue of cyber attacks, see Boothby, William H., The Law of Targeting, Oxford University Press, Oxford, 2012CrossRefGoogle Scholar.

33 See, e.g., US Law of War Manual, above note 10, para. 16.5.2.

34 Melzer, Nils, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law, ICRC, Geneva, 2009Google Scholar (ICRC Interpretive Guidance), p. 49.

35 Tallinn Manual 2.0, above note 6, Rule 92.

36 Ibid., p. 419.

37 Ibid., p. 417. See also C. Droege, above note 11, pp. 560–561.

38 Tallinn Manual 2.0, above note 6, pp. 417–418. On the loss of functionality, see W. Boothby, above note 32, pp. 386–387.

39 Tallinn Manual 2.0, above note 6, p. 418.

40 Ibid.

41 Ibid. See also ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, October 2015 (2015 Challenges Report), pp. 41-42, available at: www.icrc.org/en/document/international-humanitarian-law-and-challenges-contemporary-armed-conflicts.

42 ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, October 2011, p. 38, available at: www.icrc.org/eng/assets/files/red-cross-crescent-movement/31st-international-conference/31-int-conference-ihl-challenges-report-11-5-1-2-en.pdf; 2015 Challenges Report, above note 41, pp. 41–42

43 2015 Challenges Report, above note 41, p. 41.

44 Ibid.

45 Ibid.

46 Ibid., p. 42.

47 Ibid., pp. 41–42.

48 It must be cautioned that the debate does not extend to a cyber operation directed at data when that operation has knock-on destructive or injurious effects. Consider a cyber operation that deletes or manipulates data in an air traffic control system and thereby risks the crash of aircraft. There is broad consensus that such an operation would be an attack. The data issue only arises in situations in which a cyber operation against data does not risk having consequences that otherwise would qualify it as an attack.

49 Operations directed against certain data are prohibited by other IHL rules. See, e.g., Tallinn Manual 2.0, above note 6, Rule 132 and discussion at p. 515 (medical data), and Rule 142 and discussion at pp. 535–536 (some experts extend protection to cultural property in data form).

50 Ibid., p. 437.

51 Vienna Convention on the Law of Treaties, 1155 UNTS 331, 23 May 1969 (entered into force 27 January 1980), Art. 31(1).

52 Sandoz, Yves, Swinarski, Christophe and Zimmerman, Bruno (eds), Commentary on the Additional Protocols, ICRC, Geneva, 1987Google Scholar (ICRC Commentary on APs), paras 2007–2008: “The English text uses the word ‘objects’, which means ‘something placed before the eyes, or presented to the sight or other sense, an individual thing seen, or perceived, or that may be seen or perceived; a material thing’. … The French … text uses the word ‘biens’, which means ‘chose tangible, susceptible d'appropriation’. It is clear that in both English and French the word means something that is visible and tangible.” It must be acknowledged that the context in which this explanation was offered is not directly applicable, but the Tallinn Manual experts nevertheless found it helpful in their deliberations.

53 Tallinn Manual 2.0, above note 6, pp. 437.

54 2015 Challenges Report, above note 41, p. 43.

55 Ibid.

56 Dinniss, Heather A. Harrison, “The Nature of Objects: Targeting Networks and the Challenge of Defining Cyber Military Objectives”, Israel Law Review, Vol. 48, No. 1, 2015Google Scholar.

57 Ibid., pp. 41–49.

58 Mačák, Kubo, “Military Objectives 2.0: The Case for Interpreting Computer Data as Objects under International Humanitarian Law”, Israel Law Review, Vol. 58, No. 1, 2015, p. 55CrossRefGoogle Scholar. I responded to both approaches in “The Notion of ‘Objects’ during Cyber Operations: A Riposte in Defence of Interpretive Precision”, Israel Law Review, Vol. 48, No. 1, 2015.

59 K. Mačák, above note 58, p. 80.

60 See generally, e.g., US Joint Chiefs of Staff, Information Operations, Joint Publication 3-13, as amended 20 November 2014.

61 See, e.g., US Army, Counterinsurgency, Field Manual 3-24, December 2006, paras 5-19–5-34.

62 The US military is carefully assessing the use of such capabilities. See, e.g., II, Liston Wells, “Cognitive-Emotional Conflict: Adversary Will and Social Resilience”, Prism, Vol. 7, No. 2, 2017Google Scholar. Prism is published by the US National Defense University. The emphasis on such operations is evidenced by establishment of the College of Information and Cyberspace at National Defense University (website available at: http://cic.ndu.edu/).

63 US Department of War, Instructions for the Government of Armies of the United States in the Field, General Order No. 100, 24 April 1863 (Lieber Code), Art. 16.

64 Declaration Renouncing the Use, in Time of War, of Explosive Projectiles Under 400 Grammes Weight, Martens Nouveau Recueil, Series 1, Vol. 18, 29 November 1868, Preamble.

65 ICJ, Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion, 9 July 2004, ICJ Reports 2004, p. 172; ICJ, Nuclear Weapons, above note 8, p. 257. The Nuremberg Tribunal also found that the rules set forth in Hague Convention IV reflect customary law: see Trial of the Major War Criminals before the International Military Tribunal, Vol. 1, 1947, p. 254.

66 Convention (IV) Respecting the Laws and Customs of War on Land, 36 Stat. 2277, 207 Consol. T.S. 277, 18 October 1907 (Hague Convention IV), Preamble. See also Convention (II) with Respect to the Laws and Customs of War on Land, 32 Stat. 1803, Martens Nouveau Recueil, Series 2, Vol. 26, 29 July 1899, Preamble. The 1899 and 1907 Hague Regulations, in Article 22 of the Annex to both treaties, also note: “The right of belligerents to adopt means of injuring the enemy is not unlimited.” For the modern expression of this principle, see AP I, Art. 35(1) (adding a reference to “methods” of warfare).

67 Hague Convention IV, Preamble; AP I, Art. 1(2). The clause has been cited by in ICJ, Nuclear Weapons, above note 8, p. 257.

68 ICJ, Corfu Channel (United Kingdom v. Albania), 9 April 1949, ICJ Reports 1949, p. 22.

69 This cognitive paradigm of physicality finds expression, for example, in the general principle that the “civilian population and individual civilians shall enjoy general protection against dangers arising from military operations” (AP I, Art. 51(1), emphasis added); the reference to violence in the definition of attack (Art. 49(1)); the limitation in the application of the rule proportionality and certain precautions in attack to “incidental loss of civilian life, injury to civilians, [and] damage to civilian objects” (Arts 51(5)(b), 57(2)(a)(ii), 51(2)(a)(iii), 51(2)(b), emphasis added); and the prohibition of “acts or threats of violence the primary purpose of which is to spread terror among the civilian population” (Art. 51(2), emphasis added). Indeed, in explicating the principle of distinction, which requires that parties to a conflict “at all times distinguish between the civilian population and combatants and between civilian objects and military objectives and accordingly … direct their operations only against military objectives” (Art. 48), the ICRC Commentary to the Additional Protocols defines military operations as those “during which violence is used” (ICRC Commentary on APs, above note 52, para. 1875, emphasis added).

70 Schmitt, Michael N., “The Law of Cyber Warfare: Quo Vadis?”, Stanford Law and Policy Review, Vol. 25, No. 2, 2014Google Scholar.

71 Ibid., p. 296.

72 For an early proposal along these lines, see Adam Segal, “Cyber Space Governance: The Next Step”, Council on Foreign Relations, Policy Innovation Memorandum No. 2, 14 November 2011, p. 3, available at: www.cfr.org/cybersecurity/cyberspace-governance-next-step/p24397. A number of authors have expressed scepticism about the prospects of this proposal: see C. Droege, above note 11, p. 577; Geiss, Robin and Lahmann, Henning, “Cyber Warfare: Applying the Principle of Distinction in an Interconnected Space”, Israel Law Review, Vol. 45, No. 3, 2012, p. 394CrossRefGoogle Scholar. I am less pessimistic than these authors about the prospect of States issuing such declarations or policies regarding so-called “digital safe havens”, but believe the proposal, which encompassed both jus ad bellum and jus in bello issues, requires greater legal granularity.

73 Tallinn Manual 2.0, above note 6, Rule 131 (the duty to “respect” is “breached by actions that impede or prevent medical or religious personnel, units, or medical transports from performing their medical or religious functions”: Ibid., p. 514). For the obligations generally, see Geneva Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, of 12 August 1949, 75 UNTS 31 (entered into force 21 October 1950), Arts 19, 24, 25, 35–36; Geneva Convention (II) for the Amelioration of the Condition of the Wounded, Sick, and Shipwrecked Members of Armed Forces at Sea of 12 August 1949, 75 UNTS 85 (entered into force 21 October 1950), Arts 22, 24, 25, 27, 36–39; Geneva Convention (III) relative to the Treatment of Prisoners of War of 12 August 1949, 75 UNTS 135 (entered into force 21 October 1950), Art. 33; Geneva Convention (IV) relative to the Protection of Civilian Persons in Time of War of 12 August 1949, 75 UNTS 287 (entered into force 21 October 1950), Arts 18–22; AP I, Arts 12, 15, 21–24, 26; AP II, Art. 9.

74 Tallinn Manual 2.0, above note 6, Rule 145. For the obligation generally, see GC IV, Arts 23, 59; AP I, Arts 69–70.

75 2015 Challenges Report, above note 41, pp. 42–43.

76 Ibid., p. 43.

77 See, e.g., John Moteff, Claudia Copeland and John Fischer, Critical Infrastructures: What Makes an Infrastructure Critical?, Congressional Research Service Report, 29 January 2003.

78 Michael N. Schmitt and Tim Maurer, “Protecting Financial Data in Cyberspace: Precedent for Further Progress on Cyber Norms?”, Just Security, 26 August 2017, available at: www.justsecurity.org/44411/protecting-financial-data-cyberspace-precedent-progress-cyber-norms/. That proposal does not encompass such activities as blocking access to data for a limited period of time or intruding into confidential data.

79 IHL's focus on physicality poses particular challenges with respect to cyber operations that do amount to an attack. In particular, the collateral damage that factors into the proportionality analysis and the requirement to take feasible precautions in attack is textually limited to injury, death or damage. Although damage can reasonably be understood to include loss of functionality (wherever that threshold might lie), it does not include other forms of harm. For example, a proportionality analysis of an attack on dual-use cyber infrastructure would not, as a matter of law, need to account for the temporary disruption or loss of civilian services that depend on it unless that loss placed civilians at risk of physical harm or civilian objects at risk of damage. While this is also the case with kinetic strikes, as with an attack on a store that is being used to stash weapons, networking and other forms of connectivity exacerbate the knock-on non-destructive or non-injurious effects of cyber-attacks. This article does not address that reality as it is limited to cyber operations falling beyond the reach of IHL, but it is a cyber-specific phenomenon that merits serious attention.

80 Tallinn Manual 2.0, above note 6, Rule 101; Harvard Program on Humanitarian Policy and Conflict Research, HPCR Manual on International Law Applicable to Air and Missile Warfare, Cambridge University Press, Cambridge, 2013 (Harvard Manual), p. 119; Melzer, Nils, International Humanitarian Law: A Comprehensive Introduction, ICRC, Geneva, 2016, p. 92Google Scholar. For a discussion of the distinctness of part of a targeted object, see Schmitt, Michael N. and Merriam, John J., “The Tyranny of Context: Israeli Targeting Practices in Legal Perspective”, University of Pennsylvania Journal of International Law, Vol. 37, No. 1, 2015, pp. 119–123Google Scholar.

81 2015 Challenges report, above note 41, p. 42.

82 See US Law of War Manual, above note 10, para. 16.5.2: “For example, even if a cyber operation is not an ‘attack’ or does not cause any injury or damage that would need to be considered under the principle of proportionality in conducting attacks, that cyber operation still should not be conducted in a way that unnecessarily causes inconvenience to civilians or neutral persons.”

83 Harvard Manual, above note 80, p. 92; Nils Melzer, Targeted Killings in International Law, Oxford University Press, Oxford, 2008, pp. 344, 360.

84 Rome Statute, above note 13, Art. 8(2)(b)(iv).

85 ICRC Commentary on APs, above note 52, para. 2209.

86 Bothe, Michael, Partsch, Karl Josef and Solf, Waldemar A., New Rules for Victims of Armed Conflicts: Commentary on the Two 1977 Protocols Additional to the Geneva Conventions of 1949, 2nd ed., Martinus Nijhoff, Leiden and Boston, MA, 2013, p. 407CrossRefGoogle Scholar. See also UK Ministry of Defence, The Manual of the Law of Armed Conflict, 2004 (UK Law of War Manual), para. 5.33.3.

87 M. Bothe, K. J. Partsch and W. A. Solf, above note 86, p. 407.

88 Harvard Manual above note 80, p. 36.

89 As noted in the UK declaration on ratification of AP I, “the military advantage anticipated from an attack is intended to refer to the advantage anticipated from the attack as a whole and not only from isolated or particular parts of the attack”. UK Additional Protocol Ratification Statement, para. (i), available at: https://tinyurl.com/yct795zh.

90 “Tactical level of warfare — The level of warfare at which battles and engagements are planned and executed to achieve military objectives assigned to tactical units or task forces”: US Department of Defense, Dictionary of Military and Associated Terms, current as of March 2018, p. 226; “Operational level of warfare — The level of warfare at which campaigns and major operations are planned, conducted, and sustained to achieve strategic objectives within theaters or other operational areas”: Ibid., p. 173; “Strategic level of warfare — The level of warfare at which a nation, often as a member of a group of nations, determines national or multinational (alliance or coalition) strategic security objectives and guidance, then develops and uses national resources to achieve those objectives”: ibid.., p. 219.

91 UK Law of War Manual, above note 86, para. 5.33.5; Harvard Manual, above note 80, pp. 36–37; Tallinn Manual 2.0, above note 6, p. 442. See also Ian Henderson, The Contemporary Law of Targeting, Martinus Nijhoff, Boston, MA, 2009, pp. 199–202, providing a more detailed discussion of why military advantage may be measured at the operational as opposed to the tactical level, and why measuring military advantage at the strategic level is generally not appropriate.

92 UK Law of War Manual, above note 86, para. 2.2.

93 Opposition to Chapter IX of the ICRC Interpretive Guidance, above note 34, arose when some experts participating in the project objected to what they considered to be use of the principle as a primary rule of law. See, e.g., Parks, W. Hays, “Part IX of the ICRC ‘Direct Participation in Hostilities’ Study: No Mandate, No Expertise, and Legally Incorrect”, New York University Journal of International Law and Politics, Vol. 42, No. 3, 2010, pp. 802–810Google Scholar. But see the reply by Nils Melzer, then of the ICRC's legal division, who led the project: 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”, New York University Journal of International Law and Politics, Vol. 42, No. 3, 2010, pp. 892–912Google Scholar.

94 Interestingly, see US Law of War Manual, above note 10, para. 16.5.2. (operations not qualifying as attacks nevertheless “must not be directed against enemy civilians or civilian objects unless the operations are militarily necessary”). This discussion has been criticized, and rightly so. See Boothby, William H. and von Heinegg, Wolff Heintschel, The Law of War: A Detailed Assessment of the Department of Defense Law of War Manual, Cambridge University Press, Cambridge, 2018CrossRefGoogle Scholar.

95 M. N. Schmitt, above note 19.

96 Interesting work in this regard is being done by Lieutenant-Colonel Bart van den Bosch (Netherlands Army) in a University of Amsterdam PhD (“Waging War Without Violence”) under the direction of Professor Terry Gill and Brigadier General Paul Duchiene.

97 See UK Law of War Manual, above note 86, para. 5.32.1 (“So the commander will have to bear in mind the effect on the civilian population of what he is planning to do and take steps to reduce that effect as much as possible”); Harvard Manual, above note 80, p. 142 (“‘Constant care’ means that there are no exceptions from the duty to seek to spare the civilian population, civilians and civilian objects”); Tallinn Manual 2.0, above note 6, p. 477 (noting the “broad general duty to ‘respect’ the civilian population, that is to consider deleterious effects of military operations on civilians”). Further, the Tallinn Manual 2.0 states that “the duty of constant care requires commanders and all others involved in the operations to be continuously sensitive to the effects of their activities on the civilian population and civilian objects, and to seek to avoid any unnecessary effects thereon” (p. 477).