1 See, for example, Shaw, Martin, The New Western Way of War (London: Polity, 2005), p. 24Google Scholar .

2 Customary international law or ‘international custom’ is one of the primary sources of international law and is derived from the consistent practice of states over time who are under the belief that their behaviour is permitted or otherwise required by law. This psychological element – called opinio juris – must be present in order for state practice to count toward the development of international custom. See, Brownlie, Ian, Principles of Public International Law, 6th edition (Oxford: Oxford University Press, 2003), pp. 6–12Google Scholar .

3 See, Stahn, Carsten, ‘Terrorist Acts as “Armed Attack”: The Right to Self-Defense, Article 51(½) of the UN Charter, and International Terrorism’, Fletcher Forum on World Affairs, 27:2 (2003), pp. 35–54Google Scholar ; Drumbl, Mark A., ‘Self-Defense and the Use of Force: Breaking the Rules, Making the Rules, or Both?’, International Studies Perspectives, 4:4 (2003), pp. 409–431Google Scholar ; Kegley, Charles W. Jr. and Raymond, Gregory A., ‘Preventive War and Permissive Normative Order’, International Studies Perspectives, 4:4 (2003), pp. 385–394Google Scholar ; Franck, Thomas M., ‘What Happens Now? The UN after Iraq’, America Journal of International Law, 97:3 (2003), p. 619Google Scholar .

4 For a useful conceptual discussion of states as legal persons, see Gould, Harry D., ‘International Criminal Bodies’, Review of International Studies, 35:3 (2009), pp. 701–721CrossRefGoogle Scholar .

5 Charter of the UN (hereafter UN Charter), Stat. 1031, 26 June 1945, Article 51.

6 See this debate as outlined in Gray, Christine, International Law and the Use of Force, 2nd edition (Oxford: Oxford University Press, 2004), pp. 98–99Google Scholar .

7 Schrijver, Nico J., ‘Responding to International Terrorism: Moving the Frontiers of International Law for “Enduring Freedom”’, Netherlands International Law Review, 48 (2001), p. 285Google Scholar . See also Ratner, Stephen R., ‘Jus ad Bellum and Jus in Bello after September 11’, American Journal of International Law, 96 (2002), p. 920Google Scholar .

8 Franck, Thomas, Recourse to Force: State Action against Threats and Armed Attacks (Cambridge: Cambridge University Press, 2002), p. 98CrossRefGoogle Scholar .

9 For example, Henkin, Louis, How Nations Behave: Law and Foreign Policy, 2nd edition (New York: Columbia University Press, 1979), p. 141Google Scholar .

10 Clark Arend, Anthony, ‘International Law and the Preemptive use of Military Force’, The Washington Quarterly, 26:2 (2003), pp. 92–93, 96Google Scholar .

11 ‘Destruction of the “Caroline“’, in Bassett Moore, John, A Digest of International Law, 1 (Washington: Government Printing Office, 1906), pp. 409–414Google Scholar .

12 Ibid., p. 412.

13 Murphy, Sean D., ‘The Doctrine of Preemptive Self-Defense’, Villanova Law Review, 50 (2005), p. 704Google Scholar . See also Record, Jeffrey, ‘The Bush Doctrine and War with Iraq’, Parameters, 33 (2003), pp. 7–9Google Scholar .

14 See, Jennings, Robert and Watts, Arthur (eds), Oppenheim's International Law, 9th edition (Oxford: Oxford University Press, 1991), p. 412Google Scholar ; Franck, , Recourse to Force, p. 107Google Scholar ; Bothe, Michael, ‘Terrorism and the Legality of Pre-emptive Force’, European Journal of International Law, 14 (2003), pp. 227, 238Google Scholar ; Murphy, , ‘Preepmtive Self-Defense’, p. 748Google Scholar .

15 The National Security Strategy of the US of America (hereafter, NSS). September 2002. Available at: {http://www.whitehouse.gov/nsc/nss.pdf}. ‘President Bush Delivers Graduation Speech at West Point’, White House News Release, Washington, DC (1 June 2002). Available at: {http://www.whitehouse.gov/news/releases/2004/05/20040524–10.html}.

16 NSS, p. 6.

17 Ibid., p. 15.

18 ‘President Bush Delivers Graduation Speech’.

19 Drumbl, , ‘Self-Defense and the Use of Force’, p. 423Google Scholar .

20 See, Yoo, John, ‘International Law and the War in Iraq’, American Journal of International Law, 97:3 (2003), pp. 563–576Google Scholar . Dinstein, Yoram, War, Aggression and Self-Defence, 4th edition (Cambridge: Cambridge University Press, 2005), pp. 294–300Google Scholar . See the discussion of these arguments in Drumbl, ‘Self-Defense and the Use of Force’, pp. 410–411.

21 Article 51 obliges states to report any self-defensive actions they take to the Security Council, with which states typically comply. See Gray, , International Lawi, pp. 101–104Google Scholar .

22 Letter Dated 20 March 2003 from the Permanent Representative of the United Kingdom of Great Britain and Northern Ireland to the UN addressed to the President of the Security Council, UN Doc. S/2003/350, 21 March 2003. Letter Dated 20 March 2003 from the Permanent Representative of the US of America to the UN addressed to the President of the Security Council, UN Doc. S/2003/351, 21 March 2003. Letter Dated 20 March 2003 from the Permanent Representative of Australia to the UN addressed to the President of the Security Council, UN Doc. S/2003/352, 21 March 2003.

23 Kegley, Charles W. Jr. and Raymond, Gregory A., After Iraq: The Imperiled America Imperium (Oxford: Oxford University Press, 2007), pp. 67, 82, 101, 140Google Scholar . See also Brzezinski, Zbigniew, ‘Terrorized by “War on Terror”’, Washington Post (25 March 2007), B01Google Scholar .

24 Neal, Terry M., ‘Bush Reverts to Liberal Rationale for Iraq War; Critics Still Oppose War Despite Hussein's Human Rights Record’, Washington Post (9 July 2003)Google Scholar ; Falk, Richard, ‘The Iraq War and the Future of International Law’, Nuclear Age Peace Foundation (19 April 2004)Google Scholar . Available at: {http://www.wagingpeace.org/articles/2004/04/19_falk_iraq-war-law.htm}; Heinze, Eric A., ‘Humanitarian Intervention and the War in Iraq: Norms, Discourse, and State Practice’, Parameters, 36:1 (2006), pp. 20–35Google Scholar .

25 See Brownlie, , Principles of Public International Law, p. 6Google Scholar ; Shaw, Malcolm N., International Law, 3rd edition (Cambridge: Grotius Publications, Ltd, 1991), p. 70Google Scholar (stating that ‘It is how states behave in practice that forms the basis of customary law…’).

26 Gray, , International Law, pp. 130–133Google Scholar .

27 The official number officially supporting the war is difficult to establish. The US claimed over 40 states were prepared to go to war in support of the US effort, though other reports suggest figures closer to 30. See Bowman, Steve, ‘Iraq: Military Operations’, in Cardosa, Amy V. (ed.), Iraq at the Crossroads (Hauppauge, NY: Nova Publishers, 2006), pp. 137–155Google Scholar . See also, Anderson, Sarah, Bennis, Phyllis, and Cavanagh, John, ‘Coalition of the Willing or Coalition of the Coerced? How the Bush Administration Influences Allies in the War in Iraq’, Institute for Policy Studies, Washington, DC (26 February 2003), p. 8Google Scholar .

28 UNSC Resolution 1483, UN Doc. S/RES/1483, 22 May 2003, stating that it ‘recogniz[es] the specific authorities, responsibilities, and obligations under applicable international law of these states [the US and UK] as occupying powers under unified command.’

29 In addition to staunch opposition by important members of the UN Security Council at the time, namely France, Russia, China, and Germany, the leaders of 52 African states issued a statement opposing the war except as a last resort, and the 116 states that comprise the Non-Aligned Movement likewise issued a statement opposing the invasion. See Anderson, , Bennis, , and Cavanagh, , ‘Coalition of the Willing’, p. 10Google Scholar .

30 Cited in Drumbl, ‘Self-Defense and the Use of Force’, p. 423.

31 See, Final Report of the National Commission on Terrorist Attacks upon the US (hereafter ‘9/11 Commission Report’) (New York: Norton, 2004), p. 66.

32 See Mjyer, Eric P. J. and White, Nigel D., ‘The Twin Towers Attack: An Unlimited Right to Self-Defence?’, Journal of Conflict and Security Law, 7:1 (2002), pp. 5–17Google Scholar ; see also Stahn, , ‘Terrorist Acts’, p. 37Google Scholar ; Gray, , International Law, p. 165Google Scholar ; Murphy, , ‘Preemptive Self-Defense’, pp. 47–51Google Scholar ; and Ratner, , ‘Jus ad Bellum’, pp. 906–911Google Scholar .

33 Bush, George W., ‘Address to the Nation on the Terrorist Attacks’, Weekly Compilation of Presidential Documents (14 September 2001), p. 1301Google Scholar .

34 UNSC, Letter from the Permanent Representative of the US of America to the UN addressed to the President of the Security Council, UN Doc. S/2001/946 (7 October 2001).

35 Ibid.

36 Cassese, Antonio, ‘The International Community's “Legal” Response to Terrorism’, International and Comparative Law Quarterly, 38:3 (1989), p. 596CrossRefGoogle Scholar .

37 Case Concerning Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. US of America), (Merits), Judgment, 27 June 1986, ICJ Rep. 14 (hereafter “Nicaragua”), para. 195.

38 Ibid.

39 While this is the standard for attribution commonly associated with Nicaragua, the Court here was using this test to determine whether war crimes committed by the contras could be attributed to the US. Nicaragua, para. 109.

40 Ibid., para. 115.

41 Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion, 9 July 2004, ICJ Rep. 131 (hereafter ‘Wall’), para. 139; Case Concerning Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v. Uganda), (Merits) Judgment, 19 December 2005, ICJ Rep 116 (hereafter ‘DRC v. Uganda’), para, 146.

42 Draft Articles on the Responsibility of States for Internationally Wrongful Acts (hereafter ‘Draft Articles’), Report of the International Law Commission, 53rd Session (2001), Supplement No. 10 (A/56/10), chp.IV.E.1, Article 8.

43 9/11 Commission Report, chaps 5, 7. Glennon, Michael J., ‘The Fog of Law: Self-Defense, Inherence, and Incoherence in Article 51 of the UN Charter’, Harvard Journal of Law and Public Policy, 25:2 (2002), pp. 539–558Google Scholar ; see also Quigley, John, ‘The Afghanistan War and Self-Defense’, Valparaiso University Law Review, 37:2 (2003), pp. 545–546Google Scholar , and Drumbl, Mark A., ‘Victimhood in Our Neighborhood: Terrorist Crime, Taliban Guilt, and the Asymmetries of the International Legal Order’, North Carolina Law Review, 81:1 (2002), pp. 34–40Google Scholar .

44 UNSC Res. 1368, 12 September 2001, UN Doc. S/Res/1369; and UNSC Res. 1373, 28 September 2001, UN Doc. S/Res/1373.

45 North Atlantic Treaty Organization (NATO), Statement by the North Atlantic Council, 12 September 2001, Press Release (2001)124, available at: {http://www.nato.int/docu/pr/2001/p01–124e.htm}.

46 Organization of America States (OAS), Strengthening Hemispheric Cooperation to Prevent, Combat, and Eliminate Terrorism, 21 September 2001, OAS Res. RC.23/RES.1/01, para. 3.

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56 Nicaragua, para. 19.

57 DRC v. Uganda, paras 146, 147.

58 Ibid., para. 147.

59 NATO, Statement by the North Atlantic Council.

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65 DRC v. Uganda, Separate Opinion of Judge Simma, para 11.

66 Elizabeth Wilmshurst, ‘Principles on International Law on the Use of Force by States in Self-Defence’, Chatham House, Royal Institute of International Affairs (October 2005), p. 11.

67 Stahn, ‘Terrorist Acts’, p. 45. As the ICJ held in Nicaragua, ‘the prohibition of armed attacks may apply to the sending by a State of armed bands to the territory of another state, if such an operation, because of its scale and effects, would have been classified as an armed attack […] had it been carried out by regular armed forces’. Nicaragua, para. 195.

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69 Ibid., pp. 94–101.

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72 Common Article 3; Additional Protocol II, Article 1(1); see also Pictet, Jean S. (ed.), Commentary IV Geneva Convention Relative to the Protection of Civilian Persons in Times of War (International Committee of the Red Cross: Geneva, 1958), pp. 34–35Google Scholar .

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77 Ibid., pp. 10, 151.

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