1 US Department of Defense (DoD), Law of War Manual, 2015, p. 17, para. 1.4.2.1.

2 Watts, Sean, “Humanitarian Logic and the Law of Siege: A Study of the Oxford Guidance on Relief Actions”, International Law Studies, Vol. 95, 2019, p. 4Google Scholar.

3 Emanuela-Chiara Gillard, Sieges, the Law and Protecting Civilians, Chatham House Briefing, June 2019, p. 2; Gloria Gaggioli, “Are Sieges Prohibited under Contemporary IHL?”, EJIL: Talk!, 30 January 2019, available at: www.ejiltalk.org/joint-blog-series-on-international-law-and-armed-conflict-are-sieges-prohibited-under-contemporary-ihl/#more-16877 (all internet references were accessed in October 2021); Fox, Amos C., “The Reemergence of the Siege: An Assessment of Trends in Modern Land Warfare”, Landpower Essay, Vol. 18, No. 2, 2018, p. 3Google Scholar.

4 International Independent Commission of Inquiry on the Syrian Arab Republic (IICI Syria), Sieges as a Weapon of War: Encircle, Starve, Surrender, Evacuate, policy paper, 29 May 2018; IICI Syria, The Siege and Recapture of Eastern Ghouta, conference room paper, UN Doc. A/HRC/38/CRP.3, 20 June 2018; Amnesty International, Left to Die under Siege: War Crimes and Human Rights Abuses in Eastern Ghouta, Syria, 2015. With regard to Yemen, see Report of the Detailed Findings of the Group of Eminent International and Regional Experts on Yemen, UN Doc. A/HRC/42/CRP.1, 3 September 2019 (Yemen Report), pp. 82–86, paras 345–358.

5 The UN Security Council has repeatedly called upon all parties to “immediately lift the sieges of populated areas” and demanded that “all parties allow the delivery of humanitarian assistance … and enable the rapid, safe and unhindered evacuation of all civilians who wish to leave”. UNSC Res. 2139, 22 February 2014; UNSC Res. 2401, 24 February 2018.

6 International Committee of the Red Cross (ICRC), I Saw My City Die: Voices from the Front Lines of Urban Conflict in Iraq, Syria and Yemen, Geneva, 12 June 2020, pp. 40–43; ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, November 2019 (2019 Challenges Report), p. 16; Laurent Gisel, Pilar Gimeno Sarciada, Ken Hume and Abby Zeith, “Urban Warfare: An Age-Old Problem in Need of New Solutions”, Humanitarian Law and Policy Blog, 27 April 2021, available at: https://blogs.icrc.org/law-and-policy/2021/04/27/urban-warfare/.

7 Yves Sandoz, Christophe Swinarski and Bruno Zimmermann (eds.), Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949, ICRC, Geneva, 1987 (ICRC Commentary on the APs), pp. 654, 1457, paras 2094, 4797.

8 Since 2011 the ICRC has repeatedly expressed the opinion that “due to the significant likelihood of indiscriminate effects and despite the absence of an express legal prohibition for specific types of weapons, … explosive weapons with a wide impact area should be avoided in densely populated areas”. ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, October 2011 (2011 Challenges Report), p. 42. See also ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, October 2015 (2015 Challenges Report), p. 49; 2019 Challenges Report, above note 6, p. 21.

9 ICRC, Explosive Weapons in Populated Areas: Humanitarian, Legal, Technical and Military Aspects, Report of the Expert Meeting, 22 February 2015, pp. 21–23; Robinson, Isabel and Nohle, Ellen, “Proportionality and Precautions in Attack: The Reverberating Effects of Using Explosive Weapons in Populated Areas”, International Review of the Red Cross, Vol. 98, No. 1, 2016CrossRefGoogle Scholar.

10 E.-C. Gillard, above note 3, p. 2; G. Gaggioli, above note 3.

11 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 (entered into force 7 December 1978) (AP I), Art. 54(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 (entered into force 7 December 1978) (AP II), Art. 14. Applicable as customary IHL (CIHL) in both international armed conflicts (IACs) and non-international armed conflicts (NIACs). See Jean-Marie Henckaerts and Louise Doswald-Beck, Customary International Humanitarian Law, Vol. 1: Rules, Cambridge University Press, Cambridge, 2005 (ICRC Customary Law Study), pp. 186–189, available at: https://ihl-databases.icrc.org/customary-ihl/eng/docs/v1.

12 This position is articulated in the ICRC Customary Law Study, above note 11, p. 188. See also ICRC Commentary on the APs, above note 7, p. 653, paras 2089–2090: “This rule was laid down for the benefit of civilians. Consequently, the use of blockade and siege as methods of warfare remain[s] legitimate, provided they are directed exclusively against combatants.”

13 AP I, Art. 70; AP II, Art. 18. Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 193–200. The rules regulating humanitarian relief operations come into play when civilians are facing a lower level of deprivation than “starvation”. See Akande, Dapo and Gillard, Emanuela-Chiara, “Conflict-Induced Food Insecurity and the War Crime of Starvation of Civilians as a Method of Warfare: The Underlying Rules of International Humanitarian Law”, Journal of International Criminal Justice, Vol. 17, No. 4, 2019, p. 770CrossRefGoogle Scholar; E.-C. Gillard, above note 3, p. 11.

14 Another approach, which will not be addressed in this article, lies in the prohibition against indiscriminate methods of warfare. See, for example, Mark Lattimer, “Can Incidental Starvation of Civilians Be Lawful under IHL?”, EJIL: Talk!, 26 March 2019, available at: www.ejiltalk.org/can-incidental-starvation-of-civilians-be-lawful-under-ihl/; Gloria Gaggioli, “Besieging Cities and Humanitarian Access: How to Accommodate Humanitarian Needs, Legal Obligations and Operational Constraints?”, Proceedings of the Bruges Colloquium: Legal Challenges for Protecting and Assisting in Current Armed Conflicts, October 2019, pp. 129–130.

15 AP I, Art. 51(5)(b). Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 46–50.

16 Hampson asserts that sieges are like an elephant: “you know it when you see it, but you have a problem defining it”. See Steven Hill, Françoise Hampson and Sean Watts, “Can Siege Warfare Still Be Legal?”, Proceedings of the Bruges Colloquium: Urban Warfare, October 2015, p. 91.

17 Djukić, Dražan and Pons, Niccolò, The Companion to International Humanitarian Law, Brill Nijhoff, Leiden and Boston, MA, 2018, p. 645CrossRefGoogle Scholar; James Kraska, “Siege”, in Rüdiger Wolfrum (ed.), Max Planck Encyclopedia of Public International Law, December 2009, para. 1.

18 DoD, above note 1, p. 312, para. 5.19.1; US Department of the Army, Urban Operations, Field Manual 3-06, 2006, paras 6.12–6.14; Yoram Dinstein, The Conduct of Hostilities under the Law of International Armed Conflict, 3rd ed., Cambridge University Press, Cambridge, 2016, p. 253, para. 688; Sean Watts, Under Siege: International Humanitarian Law and Security Council Practice concerning Urban Siege Operations, Counterterrorism and Humanitarian Engagement Project, Harvard Law School Project on Law and Security, May 2014, p. 3.

19 2019 Challenges Report, above note 6, pp. 22–23; E.-C. Gillard, above note 3; A. C. Fox, above note 3, p. 2; J. Kraska, above note 17.

20 A. C. Fox, above note 3, pp. 3–4; Beehner, Lionel M., Berti, Benedetta and Jackson, Michael T., “The Strategic Logic of Sieges in Counterinsurgencies”, Parameters: The US Army War College Quarterly, Vol. 47, No. 2, 2017, pp. 80–81Google Scholar; S. Hill, F. Hampson and S. Watts, above note 16, p. 95; S. Watts, above note 18, p. 2.

21 2019 Challenges Report, above note 6, pp. 16–18; Durhin, Nathalie, “Protecting Civilians in Urban Areas: A Military Perspective on the Application of International Humanitarian Law”, International Review of the Red Cross, Vol. 98, No. 1, 2017, pp. 178–179Google Scholar.

22 2019 Challenges Report, above note 6, p. 23; S. Watts, above note 2, p. 14; A. C. Fox, above note 3, pp. 3–4; L. M. Beehner, B. Berti and M. T. Jackson, above note 20, pp. 80–81.

23 AP I, Art. 57(2)(ii). Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 56–58.

24 DoD, above note 1, p. 315, para. 5.20.1; Sassòli, Marco, International Humanitarian Law: Rules, Controversies and Solutions to Problems Arising in Warfare, Edward Elgar, Cheltenham, 2019, p. 575, para. 10.199CrossRefGoogle Scholar; Casey-Maslen, Stuart and Haines, Steven, Hague Law Interpreted: The Conduct of Hostilities under the Law of Armed Conflict, Hart, Oxford, 2018, p. 244Google Scholar.

25 AP I, Art. 54(1); AP II, Art. 14. Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 186–189.

26 ICRC Commentary on the APs, above note 7, p. 653, para. 2091.

27 According to Fleck, “this rule completely outlaws traditional warfare methods, such as sieges of defended towns”. Fleck, Dieter, The Handbook of International Humanitarian Law, Oxford University Press, Oxford, 2021, p. 226Google Scholar. Dinstein shares the same opinion but critically adds that “a broad injunction against sieges involving civilians is unrealistic, in view of the fact that there may be no other method of warfare to bring about the capture of a defended town with a tenacious garrison and impregnable fortifications”. According to him, “the practice of States does not confirm a sweeping abolition of siege warfare affecting civilians. Possibly, a pragmatic construction of the language of Article 54 will be arrived at, whereby siege warfare will continue to be acquiesced with – notwithstanding civilian privations – at least in those circumstances when the besieging Belligerent Party is willing to assure civilians a safe passage out.” See Yoram Dinstein, above note 18, pp. 255, 256–257, paras 695, 699; Dinstein, Yoram, “Siege Warfare and the Starvation of Civilians”, in Delissen, Astrid J. M. and Tanja, Gerard J. (eds), Humanitarian Law of Armed Conflict: Challenges Ahead: Essays in Honour of Frits Kalshoven, Martinus Nijhoff, Dordrecht and Boston, MA, 1991, pp. 151–152Google Scholar.

28 See above note 12.

29 Additional support for this narrow interpretation may be found in Article 54(2) of AP I, which provides an example of a violation of the prohibition against starvation and refers to the destruction of objects indispensable to the survival of the civilian population “for the specific purpose” of denying them for their sustenance value to the civilian population. See D. Akande and E.-C. Gillard, above note 13, p. 761; E.-C. Gillard, above note 3, p. 10.

30 ICRC Commentary on the APs, above note 7, p. 653, paras 2089–2090.

31 DoD, above note 1, pp. 315–316, paras 5.20.1–5.20.2: “Starvation specifically directed against the enemy civilian population … is prohibited.” UK Ministry of Defence (MoD), The Joint Service Manual of the Law of Armed Conflict, 2004, p. 74, para. 5.27.2: “The law is not violated if military operations are not intended to cause starvation but have that incidental effect, for example, by cutting off enemy supply routes which are also used for the transportation of food, or if civilians through fear of military operations abandon agricultural land or are not prepared to risk bringing food supplies into areas where fighting is going on.” Article 102(a) of the San Remo Manual and Article 157(a) of the Harvard Manual even refer more restrictively to, respectively, the “sole purpose” and the “sole or primary purpose” of the blockade. See Louise Doswald-Beck (ed.), San Remo Manual on International Law Applicable to Armed Conflicts at Sea, Cambridge University Press, Cambridge, 1995 (San Remo Manual), p. 179; Program on Humanitarian Policy and Conflict Research at Harvard University (HPCR), HPCR Manual on International Law Applicable to Air and Missile Warfare, Cambridge University Press, Cambridge, 2013 (Harvard Manual), p. 50.

32 Dannenbaum, Tom, “Encirclement, Deprivation and Humanity: Revising the San Remo Manual Provisions on Blockade”, International Law Studies, Vol. 97, 2021, pp. 364–365Google Scholar. See, similarly, D. Akande and E.-C. Gillard, above note 13, p. 765.

33 Dannenbaum proposes to amend Article 102(a) of the San Remo Manual as follows: “The declaration or establishment of a blockade is prohibited if it has the purpose or foreseeable consequence of starving the civilian population by depriving it of objects essential for its survival.” T. Dannenbaum, above note 32, pp. 364–369, 385.

34 The ICRC Commentary on AP I states: “It should be emphasized that the object of a blockade is to deprive the adversary of supplies needed to conduct hostilities, and not to starve civilians. Unfortunately, it is a well-known fact that all too often civilians, and above all children, suffer most as a result. If the effects of the blockade lead to such results, reference should be made to Art. 70 AP I.” ICRC Commentary on the APs, above note 7, p. 654, para. 2095. As pointed out in note 13 above, the rules regulating humanitarian relief operations come into play when civilians are facing a lower level of deprivation than “starvation”. See D. Akande and E.-C. Gillard, above note 13, p. 770; E.-C. Gillard, above note 3, p. 11.

35 E.-C. Gillard, above note 3, p. 11. See also M. Sassòli, above note 24, p. 575, para. 10.201.

36 AP I, Art. 70; AP II, Art. 18. Applicable as CIHL in IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 193–200.

37 ICRC Commentary on the APs, above note 7, p. 654, para. 2096. Geneva Convention IV already contained a strong recommendation to conclude agreements for the evacuation of certain vulnerable categories of civilians from besieged and encircled areas: see 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) (GC IV), Art. 17.

38 The prohibition against arbitrary withholding of consent is derived from (1) the need to provide an effective interpretation of the relevant treaty texts, which gives effect to all aspects of those provisions and does not render parts of them redundant; (2) the intention of those who negotiated the Additional Protocols, as reflected in the drafting history of the provisions; and (3) practice subsequent to the adoption of the Protocols. See Dapo Akande and Emanuela-Chiara Gillard, Oxford Guidance on the Law Relating to Humanitarian Relief Operations in Situations of Armed Conflict, 26 October 2016 (Oxford Guidance), pp. 21–22, paras 43–49; Akande, Dapo and Gillard, Emanuela-Chiara, “Arbitrary Withholding of Consent to Humanitarian Relief Operations in Armed Conflict”, International Law Studies, Vol. 92, 2016, p. 489Google Scholar; ICRC Customary Law Study, above note 11, pp. 196–197. The ICRC Commentary on AP I emphasizes a passage by the German delegate Professor Michael Bothe from the Official Records of the Diplomatic Conference: “[The consent reservation in Article 70 of AP I] did not imply that the Parties concerned had absolute and unlimited freedom to refuse their agreement to relief actions. A Party refusing its agreement must do so for valid reasons, not for arbitrary or capricious ones.” ICRC Commentary on the APs, above note 7, p. 819, para. 2805. However, it must be noted that this interpretation has met with resistance in scholarly writings – see the main text at note 40 below.

39 Oxford Guidance, above note 38, pp. 23–25, paras 50–54.

40 S. Watts, above note 2, p. 46.

41 Ibid., p. 22.

42 Moreover, withholding consent to medical relief operations, including on the grounds that medical supplies and equipment could be used to treat wounded enemy combatants or fighters, would be arbitrary since it amounts to a violation of the fundamental rule that the wounded and sick – including enemy combatants or fighters – must receive, to the fullest extent practicable and with the least possible delay, the medical care required by their condition (see, for example, AP I, Art. 10; AP II, Art. 7). See Oxford Guidance, above note 38, p. 23, para. 51; D. Akande and E.-C. Gillard, “Arbitrary Withholding of Consent”, above note 38, p. 496; M. Sassòli, above note 24, pp. 579–580, para. 10.210.

43 Oxford Guidance, above note 38, p. 23, para. 51.

44 2019 Challenges Report, above note 6, pp. 24–25; ICRC Customary Law Study, above note 11, p. 197.

45 Danish Ministry of Defence, Military Manual on International Law relevant to Danish Armed Forces in International Operations, 2020, p. 419: “Furthermore, it is important that the civilian population is not forced against its will to remain in the besieged town but has a chance to leave it. Only if the civilian population has received an offer to leave the town but nevertheless chooses to stay may the supply of vital necessities be cut off temporarily.” MoD, above note 31, p. 88, para. 5.34.3: “The military authorities of the besieged area might decide not to agree to the evacuation of civilians or the civilians themselves might decide to stay where they are. In those circumstances, so long as the besieging commander left open his offer to allow civilians and the wounded and sick to leave the besieged area, he would be justified in preventing any supplies from reaching that area.” See also Y. Dinstein, above note 18, pp. 255–256; Y. Dinstein, above note 27, p. 151.

46 See, in particular, AP I, Art. 70(3); GC IV, Art. 23(2–5); ICRC Customary Law Study, above note 11, pp. 193–200; Oxford Guidance, above note 38, pp. 28–29, paras 65–72.

47 M. Sassòli, above note 24, p. 581, para. 10.213.

48 Michael N. Schmitt, Kieran Tinkler and Durward Johnson, “The UN Yemen Report and Siege Warfare”, Just Security, 12 September 2019, available at: www.justsecurity.org/66137/the-un-yemen-report-and-siege-warfare/. See also D. Akande and E.-C. Gillard, “Arbitrary Withholding of Consent”, above note 38; Michael Bothe, Karl Josef Partsch and Waldemar A. Solf, New Rules for Victims of Armed Conflicts: Commentary on the Two 1977 Protocols Additional to the Geneva Conventions of 1949, 2nd ed., Brill Nijhoff, Leiden and Boston, MA, 2013, p. 485; Riordan, Kevin J., “Shelling, Sniping and Starvation: The Law of Armed Conflict and the Lessons of the Siege of Sarajevo”, Victoria University of Wellington Law Review, Vol. 41, No. 2, 2010, pp. 176–177CrossRefGoogle Scholar; Stoffels, Ruth Abril, “Legal Regulation of Humanitarian Assistance in Armed Conflict: Achievements and Gaps”, International Review of the Red Cross, Vol. 86, No. 855, 2004, p. 542Google Scholar. The US and UK military manuals provide that the besieging party may deny consent when there are serious reasons for fearing that the consignments may be diverted from their destination, the control may not be effective or a definite advantage may accrue to the military efforts or economy of the enemy. DoD, above note 1, pp. 313–314, para. 5.19.3; MoD, above note 31, pp. 220–221, para. 9.12.1.

49 D. Akande and E.-C. Gillard, “Arbitrary Withholding of Consent”, above note 38, p. 499.

50 Stevoli, Margherita, “Famine as a Collateral Damage of War”, Journal of International Humanitarian Legal Studies, Vol. 11, No. 1, 2020, p. 167CrossRefGoogle Scholar; G. Gaggioli, above note 3; G. Gaggioli, above note 14, pp. 123–124.

51 M. Sassòli, above note 24, pp. 26–27, paras 3.28–3.29; S. Casey-Maslen and S. Haines, above note 24, p. 73; 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 CCD COE Publications, Tallinn, 2012, p. 285.

52 International Court of Justice, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996, p. 34, para. 75. The notion of “attack” and the fundamental distinction between “Hague law” and “Geneva law” has recently attracted considerable scholarly attention in light of the Ntaganda case law of the International Criminal Court (ICC). While the Appeals Chamber rejected the prosecutor's appeal that the notion of attack has a special meaning in relation to Articles 8(2)(e)(iv) and 8(2)(b)(ix) of the Rome Statute and is not restricted to the conduct of hostilities, three out of five judges seem to endorse the prosecution's argument of rejecting the narrow interpretation of “attack” under IHL in favour of a broader, ordinary meaning. It has been submitted that such an interpretation severs the link between the Rome Statute and the underlying IHL rules and creates overlaps between Hague and Geneva law war crimes within the Rome Statute. ICC, The Prosecutor v. Bosco Ntaganda, Case No. ICC-01/04-02/06 A A2, Judgement (Appeals Chamber), 30 March 2021, pp. 419–427, paras 1154–1168. See also Abhimanyu George Jain, “The Ntaganda Appeal Judgment and the Meaning of ‘Attack’ in Conduct of Hostilities War Crimes”, EJIL: Talk!, 2 April 2021, available at: www.ejiltalk.org/the-ntaganda-appeal-judgment-and-the-meaning-of-attack-in-conduct-of-hostilities-war-crimes/; Ori Pomson, “Ntaganda Appeals Chamber Judgement Divided on Meaning of ‘Attack’”, Articles of War, 12 May 2021, available at: www.lieber.westpoint.edu/category/attack-symposium/.

53 Several amici curiae have reiterated this in their observations to the ICC Appeals Chamber. See ICC, The Prosecutor v. Bosco Ntaganda, Case No. ICC-01/04-02/06 A2, Amicus Curiae Observations by Prof. Geoffrey S. Corn et al., Pursuant to Rule 103 of the Rules of Procedure and Evidence on the Merits of the Legal Questions Presented in “Order Inviting Expressions of Interest as Amici Curiae in Judicial Proceedings (Pursuant to Rule 103 of the Rules of Procedure and Evidence)” of 24 July 2020 (ICC-01/04-02/06-2554) (Appeals Chamber), 18 September 2020, p. 4, para. 6; ICC, The Prosecutor v. Bosco Ntaganda, Case No. ICC-01/04-02/06 A2, Amicus Curiae Observations by Prof. Roger O'Keefe, Pursuant to Rule 103 of the Rules of Procedure and Evidence on the Merits of the Legal Questions Presented in “Order Inviting Expressions of Interest as Amici Curiae in Judicial Proceedings (Pursuant to Rule 103 of the Rules of Procedure and Evidence)” of 24 July 2020 (ICC-01/04-02/06-2554) (Appeals Chamber), 17 September 2020, pp. 5–6, para. 6; M. Sassòli, above note 24, pp. 27–28, para. 3.32.

54 The prohibition against the destruction or seizure of the property of an adversary unless for reasons of imperative military necessity and the rule that all civilians and persons hors de combat must be treated humanely apply as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 175–177, 306–308.

55 ICRC Commentary on the APs, above note 7, p. 600, para. 1875; M. Sassòli, above note 24, p. 349, para. 8.295; M. N. Schmitt, above note 51, p. 285.

56 An alternative argument could be made on the basis of what Kleffner has termed “a broader notion of proportionality as a general principle of the law of armed conflict”. Kleffner, Jann K., “Military Collaterals and Ius in Bello Proportionality”, Israel Yearbook on Human Rights, Vol. 48, 2018, p. 57Google Scholar.

57 DoD, above note 1, p. 313, para. 5.19.4; Norwegian Ministry of Defence, Manual of the Law of Armed Conflict, 2013, p. 197, para. 9.8; Australian Defence Force, Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, 2006, para. 7.35; MoD, above note 31, p. 87, para. 5.34; E.-C. Gillard, above note 3, p. 4; S. Watts, above note 18, pp. 5–15.

58 E.-C. Gillard, above note 3, p. 8.

59 See, in particular, G. Gaggioli, above note 3; G. Gaggioli, above note 14, p. 127.

60 G. Gaggioli, above note 3; G. Gaggioli, above note 14, p. 127.

61 ICRC Commentary on the APs, above note 7, p. 603, para. 1880; M. Bothe, K. J. Partsch and W. A. Solf, above note 48, pp. 328–329.

62 Y. Dinstein, above note 18, pp. 2–3, para. 6; Boothby, William H., The Law of Targeting, Oxford University Press, Oxford, 2012, pp. 81, 384CrossRefGoogle Scholar; Droege, Cordula, “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, p. 557CrossRefGoogle Scholar. See also M. Bothe, K. J. Partsch and W. A. Solf, above note 48, p. 328: “Article 49 provides a definition of ‘attacks’, a term which applies to those aspects of military operations which most directly affect the safety of the civilian population and the integrity of civilian objects.”

63 With regard to chemical weapons, see International Criminal Tribunal for the former Yugoslavia (ICTY), The Prosecutor v. Duško Tadić, Case No. IT-94-1-AR72, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction (Appeals Chamber), 2 October 1995, paras 120, 124; M. N. Schmitt, above note 51, p. 290; C. Droege, above note 62, p. 557.

64 See, for example, Gisel, Laurent, Rodenhäuser, Tilman and Dörmann, Knut, “Twenty Years On: International Humanitarian Law and the Protection of Civilians against the Effects of Cyber Operations during Armed Conflicts”, International Review of the Red Cross, Vol. 102, No. 913, 2020, p. 312CrossRefGoogle Scholar; Gill, Terry D., “International Humanitarian Law Applied to Cyber-Warfare: Precautions, Proportionality and the Notion of ‘Attack’ under the Humanitarian Law of Armed Conflict”, in Tsagourias, Nicholas and Buchan, Russell (eds.), Research Handbook on International Law and Cyberspace, Edward Elgar, Cheltenham, 2015, pp. 374–375Google Scholar; Roscini, Marco, Cyber Operations and the Use of Force in International Law, Oxford University Press, Oxford, 2014, pp. 179–180CrossRefGoogle Scholar; Dinniss, Heather Harrison, Cyber Warfare and the Laws of War, Cambridge University Press, Cambridge, 2012, p. 197CrossRefGoogle Scholar; C. Droege, above note 62, p. 557; M. N. Schmitt, above note 51, pp. 290–291; Schmitt, M. N., “Wired Warfare: Computer Network Attack and Jus in Bello”, International Review of the Red Cross, Vol. 84, No. 846, 2002, p. 377Google Scholar.

65 Michael N. Schmitt (ed.), Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations, Cambridge University Press, Cambridge, 2017 (Tallinn Manual 2.0), p. 415. For a similar definition, see Dinstein, Yoram and Dahl, Arne Willy, Oslo Manual on Select Topics of the Law of Armed Conflict: Rules and Commentary, Springer, Berlin, 2020, p. 22, Rule 24CrossRefGoogle Scholar.

66 Tallinn Manual 2.0, above note 65, p. 415, para. 3.

67 ICRC, International Humanitarian Law and Cyber Operations during Armed Conflicts, ICRC position paper submitted to the Open-Ended Working Group on Developments in the Field of Information and Telecommunications in the Context of International Security and the Group of Governmental Experts on Advancing Responsible State Behaviour in Cyberspace in the Context of International Security, November 2019, p. 7; 2015 Challenges Report, above note 8, p. 41; 2011 Challenges Report, above note 8, p. 37.

68 ICC, The Prosecutor v. Bosco Ntaganda, Case No. ICC-01/04-02/06, Decision on the Confirmation of Charges (Pre-Trial Chamber II), 9 June 2014, pp. 17–18, para. 46. See also ICC, Ntaganda, Amicus Curiae Observations by Prof. Geoffrey S. Corn et al., above note 53, p. 5, para. 13: “An ‘attack’ must involve an act reasonably expected to produce physical injury or damage to a person(s) or object(s). ‘Attack’ requires the employment of force (kinetic or not) against persons or objects to produce violent consequences. Violent consequences, in turn, are understood as death or injury in the case of persons, or physical damage or destruction in the case of objects.”

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

70 For instance, civilians enjoy general protection against dangers arising from military operations (AP I, Art. 51(1)). The principle of proportionality offers protection against attacks which might be expected to result in excessive incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof (AP I, Art. 51(5)(b)). Attackers should take all feasible precautionary measures in the choice of means and methods of attack with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects (AP I, Art. 57(2)(ii)), and when a choice is possible between several military objectives for obtaining a similar military advantage, the objective which may be expected to cause the least danger to civilian lives and to civilian objects shall be selected (AP I, Art. 57(3)). See also M. N. Schmitt, above note 51, pp. 290–291; M. N. Schmitt, above note 64, pp. 377–378.

71 2015 Challenges Report, above note 8, p. 41; L. Gisel, T. Rodenhäuser and K. Dörmann, above note 64, p. 313; M. N. Schmitt, above note 51, p. 290.

72 ICC, Ntaganda, Amicus Curiae Observations by Prof. Geoffrey S. Corn et al., above note 53, p. 6, para. 15; Dick Jackson, “Motive and Control in Defining Attacks”, Articles of War, 11 November 2020, available at: www.lieber.westpoint.edu/motive-control-attacks/; Chris Jenks, “Motive Matters: The Meaning of Attack under IHL and the Rome Statute”, Opinio Juris, 26 October 2020, available at: https://opiniojuris.org/2020/10/26/motive-matters-the-meaning-of-attack-under-ihl-the-rome-statute/.

73 DoD, above note 1, p. 312, para. 5.19.1; US Department of the Army, above note 18, paras 6.12–6.14; Yoram Dinstein, above note 18, p. 253, para. 688; S. Watts, above note 18, p. 3.

74 G. Gaggioli, above note 3; G. Gaggioli, above note 14, p. 127.

75 Drew, Phillip, “Can We Starve the Civilians? Exploring the Dichotomy between the Traditional Law of Maritime Blockade and Humanitarian Initiatives”, International Law Studies, Vol. 95, 2019, p. 303Google Scholar; Phillip Drew, The Law of Maritime Blockade: Past, Present, and Future, Oxford University Press, Oxford, 2017, p. 6; Wolff Heintschel von Heinegg, “Blockade”, in Rüdiger Wolfrum (ed.), Max Planck Encyclopedia of Public International Law, October 2015, para. 1.

76 P. Drew, The Law of Maritime Blockade, above note 75, pp. 4–5; Y. Dinstein, above note 18, p. 257, para. 700; W. Heintschel von Heinegg, above note 75; von Heinegg, Wolff Heintschel, “Blockades and Interdictions”, in Weller, Marc (ed.), The Oxford Handbook of the Use of Force in International Law, Oxford University Press, Oxford, 2015, p. 927Google Scholar.

77 D. Fleck, above note 27, p. 234; Y. Dinstein, above note 18, p. 258, para. 704.

78 San Remo Manual, above note 31, Art. 102(a); Harvard Manual, above note 31, Art. 157(a).

79 San Remo Manual, above note 31, Art. 102(b); Harvard Manual, above note 31, Art. 157(b).

80 See, for example, Danish Ministry of Defence, above note 45, pp. 564, 597; US Department of the Navy, Office of the Chief of Naval Operations, The Commander's Handbook on the Law of Naval Operations, 2017, para. 7.7.2.5; Australian Defence Force, above note 57, para. 6.65; MoD, above note 31, para. 13.74; Canada, Office of the Judge Advocate General, Joint Doctrine Manual: Law of Armed Conflict at the Operational and Tactical Levels, 2001, para. 850.

81 Report of the Secretary-General's Panel of Inquiry on the 31 May 2010 Flotilla Incident, September 2011, p. 72, para. 162; Report of the International Fact-Finding Mission to Investigate Violations of International Law, Including International Humanitarian and Human Rights Law, Resulting from the Israeli Attacks on the Flotilla of Ships Carrying Humanitarian Assistance, UN Doc. A/HRC/15/21, 27 September 2010, p. 13, para. 53; Report of the Public Commission to Examine the Maritime Incident of 31 May 2010, Part 1, January 2011, pp. 90–102, paras 87–97; Report of the Commission of Inquiry on Lebanon, UN Doc. A/HRC/3/2, 23 November 2006, p. 64, para. 275.

82 HPCR, Commentary on the HPCR Manual on International Law Applicable to Air and Missile Warfare, Cambridge University Press, Cambridge, 2013, p. 297; San Remo Manual, above note 31, p. 179; T. Dannenbaum, above note 32, pp. 336–337. For the opinion that a blockade does amount to an attack in the sense of Article 49(1) of AP I, see P. Drew, The Law of Maritime Blockade, above note 75, p. 99.

83 Yemen Report, above note 4, pp. 178–179, para. 746. See also Report of the United Nations High Commissioner for Human Rights Containing the Findings of the Group of Independent Eminent International and Regional Experts and a Summary of Technical Assistance Provided by the Office of the High Commissioner to the National Commission of Inquiry, A/HRC/39/43, 17 August 2018, p. 9, para. 58: “Given the severe humanitarian impact that the de facto blockades have had on the civilian population and in the absence of any verifiable military impact, they constitute a violation of the proportionality rule of international humanitarian law.” This approach has been endorsed by Schmitt, Tinkler and Johnson, who hold that “sieges are lawful so long as directed at enemy forces (and not intended to starve the civilian population), compliant with the rule of proportionality, and consistent with the requirement to take precautions in attack”. M. N. Schmitt, K. Tinkler and D. Johnson, above note 48. Benvenisti recently made a similar argument with regard to the prolonged siege and blockade of Gaza; according to him, “the laws of siege and blockade, especially in the long run, must weigh against the military purpose of the blockade the full scope of damage – whether direct or collateral – suffered by the civilian population”. See Benvenisti, Eyal, “The International Law of Prolonged Sieges and Blockades: Gaza as a Case Study”, International Law Studies, Vol. 97, 2021, p. 981Google Scholar.

84 DoD, above note 1, pp. 315–316, paras 5.20.1–5.20.2.

85 According to the ICRC Commentary on AP I, “the entire law of armed conflict is, of course, the result of an equitable balance between the necessities of war and humanitarian requirements. There is no implicit clause in the [Geneva] Conventions which would give priority to military requirements. The principles of the Conventions are precisely aimed at determining where the limits lie; the principle of proportionality contributes to this.” ICRC Commentary on the APs, above note 7, p. 683, para. 2206. See also E.-C. Gillard, Proportionality in the Conduct of Hostilities: The Incidental Harm Side of the Assessment, Chatham House, December 2018, p. 3, para. 1; Schmitt, Michael N., “Military Necessity and Humanity in International Humanitarian Law: Preserving the Delicate Balance”, Virginia Journal of International Law, Vol. 50, No. 4, 2010, p. 804Google Scholar.

86 Michael N. Schmitt, “Targeting in Operational Law”, in Terry D. Gill and Dieter Fleck (eds.), The Handbook of the International Law of Military Operations, Oxford University Press, Oxford, 2015, p. 283, para. 16.06.

87 AP I, Art. 51(5)(b). Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 46–51.

88 Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 58–60.

89 Applicable as CIHL in both IACs and NIACs. See ibid., pp. 60–62.

90 DoD, above note 1, p. 249, para. 5.10.5.

91 Cohen, Amichai and Zlotogorski, David, Proportionality in International Humanitarian Law: Consequences, Precautions, and Procedures, Oxford University Press, Oxford, 2021, p. 3CrossRefGoogle Scholar.

92 Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign against the Federal Republic of Yugoslavia, 13 June 2000 (Yugoslavia Report), para. 48.

93 E.-C. Gillard, above note 85, p. 3, para. 2. According to Dinstein, “these difficulties are disquieting. Still, it would be wrong to believe that weighing the expected collateral damage as against the anticipated military advantage is not doable.” Y. Dinstein, above note 18, p. 159, para. 426.

94 D. Fleck, above note 27, p. 262; Schmitt, Michael N., “International Humanitarian Law and the Conduct of Hostilities”, in Saul, Ben and Akande, Dapo (eds.), The Oxford Guide to International Humanitarian Law, Oxford University Press, Oxford, 2020, p. 153Google Scholar; Y. Dinstein, above note 18, p. 157, para. 423.

95 ICTY, The Prosecutor v. Ante Gotovine et al., Case No. IT-06-90-T, Prosecution's Public Redacted Final Trial Brief (Trial Chamber), 2 August 2010, para. 549. See also ICTY, The Prosecutor v. Stanislav Galić, Case No. IT-98-29-T, Judgment (Trial Chamber), 5 December 2003, para. 58: “In determining whether an attack was proportionate it is necessary to examine whether a reasonably well-informed person in the circumstances of the actual perpetrator, making reasonable use of the information available to him or her, could have expected excessive civilian casualties to result from the attack.” M. Sassòli, above note 24, p. 362, para. 8.322; Laurent Gisel, The Principle of Proportionality in the Rules Governing the Conduct of Hostilities under International Humanitarian Law, report of the International Expert Meeting, ICRC and Université Laval, 22 June 2016, p. 57.

96 T. Dannenbaum, above note 32, p. 339.

97 Ibid., pp. 339–340;

98 P. Drew, The Law of Maritime Blockade, above note 75, p. 109.

99 T. Dannenbaum, above note 32, pp. 340–341.

100 Lieblich, Eliav, “On the Continuous and Concurrent Application of Ad Bellum and In Bello Proportionality”, in Kreß, Claus and Lawless, Robert (eds), Necessity and Proportionality in International Peace and Security Law, Oxford University Press, Oxford, 2021, pp. 69–70Google Scholar. This question also features in what Lubell and Cohen have termed “strategic proportionality” as lex ferenda and which requires an ongoing assessment of the use of force throughout the conflict, balancing the overall harm against the strategic objectives. See Noam Lubell and Amichai Cohen, “Strategic Proportionality: Limitations on the Use of Force in Modern Armed Conflicts”, International Law Studies, Vol. 96, 2020, p. 162.

101 E. Lieblich, above note 100, p. 61. See also Akande, Dapo and Liefländer, Thomas, “Clarifying Necessity, Imminence and Proportionality in the Law of Self-Defense”, American Journal of International Law, Vol. 107, No. 3, 2013, pp. 566–568CrossRefGoogle Scholar.

102 In contemporary international law, one of the foremost proponents of the “static approach” is Yoram Dinstein. See Yoram Dinstein, War, Aggression and Self-Defence, 6th ed., Cambridge University Press, Cambridge, 2017, pp. 282–283.

103 Raphaël van Steenberghe, “Proportionality under Jus ad Bellum and Jus in Bello: Clarifying Their Relationship”, Israel Law Review, Vol. 45, No. 1, 2012, p. 113; Judith Gail Gardam, “Proportionality and Force in International Law”, American Journal of International Law, Vol. 87, No. 3, 1993, p. 404; Christopher Greenwood, “The Relationship between Ius ad Bellum and Ius in Bello”, Review of International Studies, Vol. 9, 1989.

104 E. Lieblich, above note 100, p. 69.

105 Ibid.; McMahan, Jeff, “Proportionality and Time”, Ethics, Vol. 125, No. 3, 2015, pp. 701–705CrossRefGoogle Scholar.

106 A. Cohen and D. Zlotogorski, above note 91, p. 177.

107 Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 60–62.

108 Gillard argues that “the frequency with which a proportionality assessment must be conducted in the course of an attack depends on the context and nature of the attack”. E.-C. Gillard, above note 85, p. 46, para. 164. According to Cannizzaro, Article 57(2)(a)(iii) of AP I entails “an obligation to consider proportionality also in the successive phase in which the decision has already been taken or the attack has already been launched”. Cannizzaro, Enzo, “Proportionality in the Law of Armed Conflict”, in Clapham, Andrew and Gaeta, Paola (eds), The Oxford Handbook of International Law in Armed Conflict, Oxford University Press, Oxford, 2014, p. 335Google Scholar. Also see Amnesty International, NATO/ Federal Republic of Yugoslavia: “Collateral Damage” or Unlawful Killings? Violations of the Laws of War by NATO during Operation Allied Force, June 2000, p. 33: “Yet, even if the pilot was, for some reason, unable to ascertain that no train was travelling towards the bridge at the time of the first attack, he was fully aware that the train was on the bridge when he dropped the second bomb, whether smoke obscured its exact whereabouts or not. This decision to proceed with the second attack appears to have violated Article 57 of Protocol I which requires an attack to be cancelled or suspended if it becomes clear that the objective is a not a military one … or that the attack may be expected to cause incidental loss of civilian life … which would be excessive in relation to the concrete and direct military advantage anticipated.”

109 G. Gaggioli, above note 3; G. Gaggioli, above note 14, p. 129. This approach of continuous monitoring of proportionality has also been advocated by a number of scholars in the context of blockades. See Amichai Cohen and Yuval Shany, “The Turkel Commission's Flotilla Report (Part One): Some Critical Remarks”, EJIL: Talk!, 28 January 2011, available at: www.ejiltalk.org/the-turkel-commissions-flotilla-report-part-one-some-critical-remarks/; Matthew L. Tucker, “Mitigating Collateral Damage to the Natural Environment in Naval Warfare: An Examination of the Israeli Naval Blockade of 2006”, Naval Law Review, Vol. 57, 2009, p. 177.

110 Applicable as CIHL in both IACs and NIACs. See ICRC Customary Law Study, above note 11, pp. 58–60.

111 Yugoslavia Report, above note 92, para. 29. According to Gillard, “[t]he report was probably referring to the first part of Art. 57(2)(a)(i) AP I, which requires belligerents to verify that the objectives to be attacked are not civilian. However, the obligation to verify also requires them to ensure the attack would not violate the rule of proportionality.” E.-C. Gillard, above note 85, p. 47, para. 168.

112 E.-C. Gillard, above note 85, p. 47, para. 168; L. Gisel, above note 95, p. 48; I. Robinson and E. Nohle, above note 9, pp. 120–121. Horowitz notes: “Putting in place civilian harm complaint and investigation mechanisms, as well as ensuring they are properly resourced, ha[s] also been proven to improve civilian harm mitigation techniques.” Jonathan Horowitz, “Precautionary Measures in Urban Warfare: A Commander's Obligation to Obtain Information”, Humanitarian Law and Policy Blog, 10 January 2019, available at: https://blogs.icrc.org/law-and-policy/2019/01/10/joint-blog-series-precautionary-measures-urban-warfare-commander-s-obligation-obtain-information/.

113 L. Gisel, above note 95, p. 48.

114 See, for example, European Union Military Committee, Avoiding and Minimizing Collateral Damage in EU-Led Military Operations Concept, 3 February 2016, p. 14, paras 47–50; DoD, above note 1, pp. 252–253, para. 5.11.1.3; US Department of the Army, Protection of Civilians, Army Techniques Publication 3-07.6, 2015, p. 5.58–5.59; Australian Defence Force, Targeting, Australian Defence Doctrine Publication 3.14, 2009, para. 4.32; E.-C. Gillard, above note 85, p. 49, para. 172.

115 E.-C. Gillard, above note 85, pp. 48–49, paras 171–173.

116 ICTY, Galić, above note 95, fn. 109; M. N. Schmitt, above note 94, p. 153; M. Sassòli, above note 24, p. 362, para. 8.322; Y. Dinstein, above note 18, p. 157, para. 423; Henderson, Ian, The Contemporary Law of Targeting: Military Objectives, Proportionality and Precautions in Attack under Additional Protocol I, Martinus Nijhoff, Leiden and Boston, MA, 2009, p. 226CrossRefGoogle Scholar.

117 However, note the subtle but significant difference in both the San Remo Manual and Harvard Manual, which require comparing whether the damage or suffering to the civilian population “is, or may be expected to be”, excessive in relation to the concrete and direct military advantage anticipated from the blockade. San Remo Manual, above note 31, Art. 102(b); Harvard Manual, above note 31, Art. 157(b) (emphasis added).

118 I. Robinson and Ellen Nohle, above note 9, pp. 124–125.

119 For an analysis of the impact of protracted armed conflict on essential urban services, see ICRC, Urban Services during Protracted Armed Conflict: A Call for a Better Approach to Assisting Affected People, Geneva, 2015, pp. 21–28; I. Robinson and E. Nohle, above note 9.

120 See the nearly identical interpretive declarations of Belgium, Canada, France, Germany, Ireland, Italy, the Netherlands, Spain, the UK, and the United States upon ratification of AP I. Jean-Marie Henckaerts and Louise Doswald-Beck (eds), Customary International Humanitarian Law, Vol. 2: Practice, Cambridge University Press, Cambridge, 2005, pp. 357–358, available at: https://ihl-databases.icrc.org/customary-ihl/eng/docs/v2. See also Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons which May Be deemed to Be Excessively Injurious or to Have Indiscriminate Effects (with Protocols I, II and III), 1342 UNTS 137, 10 October 1980 (entered into force 2 December 1983), Protocol II, Art. 3(4), and Protocol III, Art. 1(5); Quéguiner, Jean-François, “Precautions under the Law Governing the Conduct of Hostilities”, International Review of the Red Cross, Vol. 88, No. 864, 2006, p. 810CrossRefGoogle Scholar.

121 E.-C. Gillard, above note 3, p. 6. See also I. Robinson and E. Nohle, above note 9, p. 139: “An issue related to the quantity and quality of information that a commander can feasibly be expected to take into account when analyzing the expected incidental damage of an attack is the relevance of the operational context.”

122 According to Durhin, “[t]he quality of intelligence is enhanced by the physical presence of human gatherers (conventional or special forces) in the theatre of operations. In the case of ‘no boots on the ground’ operations, this human intelligence is lacking, and it is unrealistic to think that technology alone can resolve this deficiency.” N. Durhin, above note 21, p. 190.