¹ Hague Convention (IV) respecting the Laws and Customs of War on Land and its annex: Regulations concerning the Laws and Customs of War on Land (entered into force 26 January 1910) Martens Nouveau Recueil (ser 3) 461.

² Geneva Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field (entered into force 21 October 1950) 75 UNTS 31; Geneva Convention (II) for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea (entered into force 21 October 1950) 75 UNTS 85; Geneva Convention (III) relative to the Treatment of Prisoners of War (entered into force 21 October 1950) 75 UNTS 135; Geneva Convention (IV) relative to the Protection of Civilian Persons in Time of War (entered into force 21 October 1950) 75 UNTS 287; Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I) (entered into force 7 December 1978) 1125 UNTS 3 (‘Additional Protocol I’ or ‘AP I’); Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts (Protocol II) (entered into force 7 December 1978) 1125 UNTS 609 (‘Additional Protocol II’ or ‘AP II’).

³ For example, the 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 (entered into force 2 December 1983) 1342 UNTS 137 (‘Convention on Conventional Weapons’ or ‘CCW’). The CCW currently has several protocols that prohibit the use of specific conventional weapons deemed to have excessively injurious or indiscriminate effects, such as certain landmines, incendiary weapons such as napalm, and blinding lasers.

⁴ One other treaty – the Convention on the Prohibition of Military or Any Hostile Use of Environmental Modification Techniques (entered into force 5 October 1978) 1108 UNTS 151 – does include some rules that prohibit certain acts during armed conflicts that might have severe and lasting effects on civilians.

⁵ Attacks on water purification facilities are prohibited only if specifically intended to displace civilian populations: AP I (n 2) art 54(2)–(3). Unfortunately, the destruction of a dual-use drinking water facility that has the incidental but foreseeable effect of increasing civilian mortality does not violate the laws of war, although a cogent argument could be made that any foreseeable indirect civilian casualties should be included in the proportionality calculus.

⁶ AP II (n 2) art 13(1).

⁷ Of potentially innumerable examples, see Human Rights Watch, ‘Iran/Iraq: Iranian Attacks Should Not Target Iraqi Civilians’, 21 July 2010, available at http://www.hrw.org/en/news/2010/07/12/iraniraq-iranian-attacks-should-not-target-iraqi-civilians; Human Rights Watch, ‘Why They Died: Civilian Casualties in Lebanon During the 2006 War’, 5 September 2007, available at http://www.hrw.org/en/reports/2007/09/05/why-they-died/.

⁸ Specifically, the International Criminal Tribunal for Rwanda (‘ICTR’) and the International Criminal Tribunal for the Former Yugoslavia (‘ICTY’).

⁹ For example, the Special Court for Sierra Leone and the Extraordinary Chambers in the Courts of Cambodia.

¹⁰ Rome Statute of the International Criminal Court (entered into force 1 July 2002) 2187 UNTS 90 (‘ICC Statute’).

¹¹ See Arsanjani, Mahnoush H and Reisman, W Michael, ‘The Law-in-Action of the International Criminal Court’ (2005) 99 American Journal of International Law 385CrossRefGoogle Scholar.

¹² AP I (n 2) arts 51(5)(b) and 57(2)(a)(iii), (b).

¹³ See Fellmeth, Aaron Xavier, ‘Questioning Civilian Immunity’ (2008) 43 Texas International Law Journal 454, 478–91Google Scholar.

¹⁴ See generally Dinstein, Yoram, The Conduct of Hostilities under the Law of International Armed Conflict (2nd edn, CUP 2010) 132–3CrossRefGoogle Scholar. Antonio Cassese, for example, has criticised the proportionality principle for its difficulty of application: see Cassese, Antonio, ‘The Prohibition of Indiscriminate Means of Warfare’ in Akkerman, Robert J, van Krieken, Peter J and Pannenborg, Charles O (eds), Declarations on Principles: A Quest for Universal Peace (AW Sijthoff 1977) 171, 184Google Scholar.

¹⁵ cf Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia (2000) 39 International Legal Materials 1257, 1271 (‘It is much easier to formulate the principle of proportionality in general terms than it is to apply it to a particular set of circumstances’). The Proportionality Study, discussed in Section 2.3, has already uncovered a few more examples, albeit among dozens of cases of disproportionate attacks committed with impunity.

¹⁶ ICC Statute (n 10) art 8(2)(b)(iv).

¹⁷ ICTY, Prosecutor v Blaškić, Trial Judgment, IT-95-14-T, Trial Chamber, 3 March 2000, [507]–[510].

¹⁸ Dinstein (n 14) 131–32; Cohen, Amichai, ‘The Principle of Proportionality in the Context of Operation Cast Lead: Institutional Perspectives’ (2009) 35 Rutgers Law Record 23Google Scholar.

¹⁹ An indiscriminate attack is one made without any attempt to (or ability to) target a legitimate military objective and that consequently may result in civilian casualties or property damage: AP I (n 2) art 51(4). Disproportionate attacks, in contrast, are always directed toward a legitimate military objective.

²⁰ Blaškić (n 17) [507]–[510].

²¹ See AP I (n 2) arts 48 and 51(4).

²² ICTY, Prosecutor v Blaškić, Appeal Judgment, IT-95-14-A, Appeals Chamber, 29 July 2004, [441].

²³ ibid [444], [463].

²⁴ ibid [463].

²⁵ ICTY, Prosecutor v Galić, Judgment, IT-98-29-T, Trial Chamber, 5 December 2003, [372]–[387].

²⁶ Bell, Abraham, ‘Critique of the Goldstone Report and Its Treatment of International Humanitarian Law’ (2010) 104 American Society of International Law Proceedings (forthcoming)Google Scholar, available at http://ssrn.com/abstract=1581533

²⁷ ICTY, Prosecutor v Galić, Appeal Judgment, IT-98-29-A, Appeals Chamber, 30 November 2006, [134].

²⁸ See, for example, the Convention on Cluster Munitions (entered into force 1 August 2010), available at http://www.clusterconvention.org/downloadablefiles/ccm77_english.pdf. See also AP I (n 2) art 54(4) (prohibiting parties from employing indiscriminate methods of attack, including by implication using weapons that are by their nature indiscriminate); Case Concerning the Legality of the Threat or Use of Nuclear Weapons [1996] ICJ Rep 226, [95] (implying that the use of inherently indiscriminate weapons violates customary jus in bello by its statement that the use of nuclear weapons seems ‘scarcely reconcilable’ with the requirement that methods and means of warfare discriminate between military and civilian targets).

²⁹ AP I (n 2) art 51(5)(a).

³⁰ ibid art 57(3).

³¹ AP II (n 2) art 13(1).

³² See, for example, Bothe, Michael, Partsch, Karl Josef and Solf, Waldemar A, New Rules for Victims of Armed Conflicts (Martinus Nijhoff 1982) 299Google Scholar; Dinstein, Yoram, ‘Collateral Damage and the Principle of Proportionality’ in Wippman, David and Evangelista, Matthew (eds), New Wars, New Laws? (Transnational 2005) 211Google Scholar; Parks, W Hays, ‘Air War and the Law of War’ (1990) 32 Air Force Law Review 1, 168Google Scholar; Penna, LR, ‘Customary International Law and Protocol I: An Analysis of Some Provisions’ in Swinarski, Christophe (ed) Studies and Essays on International Humanitarian Law and Red Cross Principles (Kluwer Law International 1976) 201, 220Google Scholar; Mark David Maxwell and Richard V Meyer, ‘The Principle of Distinction: Probing the Limits of its Customariness’, The Army Lawyer, March 2007, Pamphlet 27-50-406, 1, 10, available at http://www.loc.gov/rr/frd/Military_Law/pdf/03-2007.pdf.

³³ See, for example, ICTY, Prosecutor v Duško Tadić, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, IT-94-1, Appeals Chamber, 2 October 1995, [127] (‘[I]t cannot be denied that customary rules have developed to govern internal strife. These rules … cover such areas as protection of civilians from hostilities, in particular from indiscriminate attacks … as well as prohibition of means of warfare proscribed in international armed conflicts and ban of certain methods of conducting hostilities.’); ICTY, Prosecutor v Kupreskić, Judgment, IT-95-16-T, Trial Chamber II, 14 January 2000, [524] (concluding that the principle of proportionality is a ‘general principle of international law’).

³⁴ Henckaerts, Jean-Marie and Doswald-Beck, Louise, Customary International Humanitarian Law, Vol I: Rules (ICRC, CUP 2005) 48–49, 58–59CrossRefGoogle Scholar. The ICRC, although a non-governmental organisation, plays a dominant role in the negotiation and interpretation of international humanitarian law. Its guidance is influential and regarded seriously by both national and international political elites.

³⁵ See, for example, Matheson, Michael J, ‘Session One: The United States Position on the Relation of Customary International Law to the 1977 Protocols Additional to the 1949 Geneva Conventions’ (1987) 2 American University Journal of International Law and Policy 419, 426Google Scholar (stating official US policy as recognising the rule of proportionality and most other provisions of AP I as customary international law). But see Hays Parks (n 32) 173 (stating that, in reviewing a draft of AP I during negotiations, the US Department of Defense concluded that the concept of proportionality was not a customary rule of law as presented in the draft).

³⁶ See, for example, Levine, Alan J, The Strategic Bombing of Germany: 1940–1945 (Praeger 1992)Google Scholar; Mountcastle, John W, Flame On! US Incendiary Weapons, 1918–1945 (White Maine Books 1999) 68–85, 103–19Google Scholar; Werrell, Kenneth P, Blankets of Fire: U.S. Bombers over Japan during World War II (Smithsonian Institution Press 1996), 150–68Google Scholar; Grayling, AC, Among the Dead Cities: The History and Moral Legacy of the WWII Bombing of Civilians in Germany and Japan (Walker 2006) 76–78Google Scholar.

³⁷ cf Oeter, Stefan, ‘Methods and Means of Combat’ in Fleck, Dieter (ed), The Handbook of Humanitarian Law in Armed Conflicts (2nd edn, OUP 2008)Google Scholar, 119, 198; Rogers, Anthony PV, ‘The Principle of Proportionality’ in Hensel, Howard M (ed), The Legitimate Use of Military Force: The Just War Tradition and the Customary Law of Armed Conflict (Ashgate 2008)Google Scholar 189, 190, 202.

³⁸ See Fellmeth (n 13) 454–55.

³⁹ See nn 29–32 and sources cited therein.

⁴⁰ The US, for example, is exceptionally open. The general rule is that courts martial are open to the public, although they may be closed at the discretion of the military judge. See Joint Service Committee on Justice, Military, Manual for Courts-Martial United States (2008 edn), II–79Google Scholar.

⁴¹ For example, Schmitt, Michael N, ‘The Law of Targeting’ in Wilmshurst, Elizabeth and Breau, Susan (eds), Perspectives on the ICRC Study on Customary International Humanitarian Law (CUP 2007)Google Scholar 131, 135, 156.

⁴² Tadić (n 33) [99].

⁴³ Art 8(2)(b)(iv) of the ICC Statute gives the court jurisdiction over an attack made ‘in the knowledge that such attack will cause incidental loss of life or injury to civilians or damage to civilian objects or widespread, long-term and severe damage to the natural environment, which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated’.

⁴⁴ See Pictet, Jean (general ed), Uhler, Oscar M and Coursier, Henri (eds), Geneva Convention Relative to the Protection of Civilian Persons in Time of War: Commentary (ICRC 1958) 46Google Scholar (observing that the reason for excluding a belligerent's own nationals from the category of ‘protected persons’ was concern to avoid interfering with a sovereign state's relationship with its own nationals); Maxwell & Meyer (n 32) 10.

⁴⁵ For example, Tadić (n 33) [119]. ‘What is inhumane, and consequently proscribed, in international wars, cannot but be inhumane and inadmissible in civil strife’: Henckaerts and Doswald-Beck (n 34) 58–59.

⁴⁶ The news media has become more effective at publicising military operations and war crimes since the spread of satellite news transmission and resource-rich global media organisations. However, information reported by the media is frequently unverified, anecdotal, or derived from the self-interested military organisations themselves.

⁴⁷ Henckaerts and Doswald-Beck (n 34).

⁴⁸ Bellinger, John B III and Haynes, William J II, ‘A US Government Response to the International Committee of the Red Cross Study Customary International Humanitarian Law’ (2007) 89 International Review of the Red Cross 443Google Scholar.

⁴⁹ ibid.

⁵⁰ See, for example, Schmitt (n 41) 134; Dinstein, Yoram, ‘The ICRC Customary International Humanitarian Law Study’ (2006) 36 Israel Yearbook on Human Rights 1Google Scholar.

⁵¹ When states wish to constrain military commanders in a specific armed conflict, they issue rules of engagement, and these may include tighter constraints on attack modalities motivated by concerns specific to the conflict at issue, such as a desire to win goodwill or avoid opprobrium among the civilian population.

⁵² At the conclusion of the Geneva Conferences of 1977, the Legal Adviser to the US Department of State publicly specified which provisions of the Additional Protocols the State Department considers to be reflective of customary international law, and which it does not: Matheson (n 35). It is possible that the US critics of the ICRC Study have erroneously assumed that this practice is a usual one. In fact, very few state governments take public positions on the customary status of a rule or principle except in the course of an international dispute directly on point.

⁵³ Pound, Roscoe, ‘Law in Books and Law in Action’ (1910) 44 American Law Review 12Google Scholar.

⁵⁴ See generally Bundell, William E, The Art and Craft of Feature Writing (Plume 1988)Google Scholar.

⁵⁵ See generally Howell, Martha C and Prevenier, Walter, From Reliable Sources: An Introduction to Historical Methods (Cornell University Press 2001)Google Scholar.

⁵⁶ See Willard, Andrew R, ‘Incidents: An Essay in Method’ (1984) 10 Yale Journal of International Law 21Google Scholar; Reisman, W Michael, ‘International Incidents: Introduction to a New Genre in the Study of International Law’ in Reisman, Michael and Willard, Andrew R (eds), International Incidents: The Law that Counts in World Politics (Princeton University Press 1988) 3CrossRefGoogle Scholar.

⁵⁷ The Study accordingly has the incidental benefit of gathering data on compliance with AP I, art 82, which requires that legal advisers be made available to military commanders.

⁵⁸ The challenge here is in separating, from disproportionate attacks, those killings that were allegedly intentional but for which the evidence was inconclusive. Some actors almost always claim that an attack resulting in significant civilian deaths was indiscriminate or intentional rather than disproportionate. Whenever any significant doubt existed regarding the substantiation of such allegations, we resolved them in favour of the assumption that the killings were accidental. This brought a larger number of incidents within the scope of the study while excluding cases in which civilians were clearly targeted in violation of the principle of discrimination.

⁵⁹ The US furnishes an excellent example; there, military units in the field include an officer from the Judge Advocate General (JAG) Corps on staff. Because both JAG Corps officers and US Army commanders are trained in the laws of war, including the principle of proportionality, the laws may be expected to exert at least some influence on targeting decisions: Jackson, Richard, Special Assistant on Law of War Matters, Army Judge Advocate General Corps, participating in ‘Empirical Approaches to the International Law of War’ (2008) 16 Willamette Journal of International Law and Dispute Resolution 386, 393–94Google Scholar.

⁶⁰ The Study has already begun to uncover evidence that at least some military organisations rely on informal sanctions in preference to criminal investigations in cases of disproportionate attack. This is also sometimes true, although to a lesser extent, in response to allegations of the intentional murder of civilians.

⁶¹ Two such reforms that, if properly implemented, could enhance the role of proportionality in protecting civilians are: (1) Hampson's suggestion of dynamically redefining proportionality to account for the relative military superiority of the state in specific conflict: Hampson, Françoise J, ‘Proportionality and Necessity in the Gulf Conflict’ (1992) 86 Proceedings of the American Society of International Law 45, 45–50Google Scholar and (2) Michael Reisman's proposal to require two-level compensation to civilians and their survivors harmed either by lawful or by disproportionate attacks: Reisman, W Michael, ‘The Lessons of Qana’ (1997) 22 Yale Journal of International Law 381, 398Google Scholar.

⁶² Isayeva v Russia (2005) 41 EHRR 39, [208]–[213]; Moiwana Village v Suriname (2005) Inter-Am Ct HR, Judgment, 15 June 2005 (Ser C) No 124, 2, 10; Las Palmeras v Colombia (2001) Inter-Am Ct HR, Judgment, 6 December 2001 (Merits), (Ser C) No 90, available at http://www.corteidh.or.cr/docs/casos/articulos/seriec_90_ing.pdf.

⁶³ Cohen (n 18) 35–36.

⁶⁴ US Chairman of the Joint Chiefs of Staff, Instruction 3121.01B, Standing Rules of Engagement (13 June 2005), unclassified portions reprinted in US Dept of the Army, Judge Advocate Generals Legal Center & School, Operational Law Handbook (International & Operational Law Dept 2009) 82–96Google Scholar.

⁶⁵ US Dept of Defense, Joint Publication 3–60, Joint Targeting, ann E, app G. The classified version is US Chairman of the Joint Chiefs of Staff, Manual 3160.01A, Joint Methodology for Estimating Collateral Damage for Conventional Weapons, Precision, Unguided, and Cluster.

⁶⁶ Even the unusually transparent US government does not track civilian casualties: see, for example, Hannah Fischer, ‘Iraqi Civilian Deaths Estimates,’ CRS Report for Congress, 27 August 2008, 1, available at http://www.fas.org/sgp/crs/mideast/RS22537.pdf.

⁶⁷ For this purpose, a methodology for judging indirect casualties would need to be established by agreement. To avoid underestimating casualty statistics, for example, increased civilian mortality caused by blockades or attacks on power plants or water purification facilities should be included, as Roscini suggests: Roscini, Marco, ‘Targeting and Contemporary Aerial Bombardment’ (2005) 54 International and Comparative Law Quarterly 411, 441CrossRefGoogle Scholar. The standard for excluding more remote causes of casualties could reference the International Law Commission, Draft Articles on Responsibility of States for Internationally Wrongful Acts (‘ILC Draft Articles’), Supp No 10, UN Doc A/56/10, November 2001.

⁶⁸ See nn 62–63 and accompanying text.

⁶⁹ See generally Carpenter, R Charli, Innocent Women and Children: Gender, Norms and the Protection of Civilians (Ashgate 2006)Google Scholar.

⁷⁰ That said, knowing the number of enemy combatant casualties can assist only indirectly for two reasons. First, the relevant consideration is military advantage rather than enemy combatants killed or wounded. These two variables are far from coextensive. Second, the principle obligates commanders to weigh the military advantage anticipated against the risk of collateral damage. In any given attack, the advantage anticipated may have little relationship with the advantage acquired.

⁷¹ Roscini (n 67).

⁷² The Articles on Responsibility of States for Internationally Wrongful Acts are curiously agnostic on the question of how to determine causation: see ILC, Draft Articles (n 67) art 2(a). However, the standard of proximate cause, which is based on the reasonable foreseeability of the casualties to the attacker, is well established in customary international law and would seem to offer the best candidate: see, for example, Trail Smelter (US v Canada) (1938, 1941) 3 RIAA 1905, 1931; Portuguese Colonies (Naulilaa Incident) (1928) 2 RIAA 1011, 1031; US-German Mixed Claims Commission, Administrative Decision No II (1923) 7 RIAA 23, 30.

⁷³ See UN Office of the High Commissioner for Human Rights, ‘Non-governmental Organisations and National Human Rights Institutions’, available at http://www.ohchr.org/EN/HRBodies/UPR/Pages/NgosNhris.aspx.

⁷⁴ ICC Statute (n 10) art 8(2)(b)(iv).

⁷⁵ In the US, the prohibition on overly vague criminal laws is a constitutional requirement: Kolender v Lawson, 461 US 352, 357 (1983). The rule of lenity further requires exoneration in case of doubt about whether a criminal statute covers the conduct in question: McNally v US, 483 US 350, 359–60 (1987).

⁷⁶ AP I (n 2) art 91; Murphy, John F, ‘Civil Liability for the Commission of International Crimes as an Alternative to Criminal Prosecution’ (1999) 12 Harvard Human Rights Journal 1Google Scholar; Reisman (n 11) 398.

⁷⁷ In his 2010 report on targeted killings, the UN Special Rapporteur on Extrajudicial, Summary or Arbitrary Executions similarly observed that states failing to share information about individuals they have killed summarily on the basis of alleged terrorist identity are operating in an ‘accountability vacuum’ that can be remedied only with greater transparency: Human Rights Council, Report of the Special Rapporteur on Extrajudicial, Summary or Arbitrary Executions, Philip Alston, Study on Targeted Killings, UN Doc A/HRC/14/24/Add.6, 28 May 2010, para 92.

⁷⁸ Brandeis, Louis D, Other People's Money and How the Bankers Use it (Frederick A Stokes Co 1914) 92Google Scholar.