¹ The term “targeted killing” here refers to the deliberate killing of specifically identified individuals who are not clearly combatants in an armed conflict under international law. This definition is itself contentious. Who, and according to what criteria, is to be defined as a combatant? How do we decide whether such persons are operating in the context of an armed conflict? These issues are themselves controversial, and so determining whether a particular killing constitutes a targeted killing is not without debate. Some in the U.S. argue that those targeted under this policy are combatants in an armed conflict—but then the killing of those persons would not be distinguishable from other killing in war, and so would not be subject to particular study as “targeted killing.” See Nils Meltzer, Targeted Killing in International Law (Oxford University Press, 2008) 3–5; David Kretzmer, “Targeted Killing of Suspected Terrorists: Extra-Judicial Executions or Legitimate Means of Defense?,” 16 The European Journal of International Law (2005) 171, 174–6; Gary Solis, “Targeted Killing and the Law of Armed Conflict,” 60 Naval War College Review (2007) 127, 127–30; and Philip Alston, “Report of the Special Rapporteur on Extrajudicial, Summary or Arbitrary Executions,” May 28, 2010, U.N. Doc. A/HRC/14/24/Add.6, 3.

² The six confirmed countries are Afghanistan, Iraq, Pakistan, Yemen, Somalia and Libya.

³ The Phoenix program included the extensive use of targeted killing to “neutralize” high-ranking members of the Viet Cong. Vietnam: Policy and Prospects, 1970: Hearings Before the Committee on Foreign Relations, on Civil Operations and Rural Development Support Program, United States Senate, (U.S. Government Printing Office, 1970).

⁴ Art. 2(4) of the U.N. Charter provides that states “shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.”

⁵ Mary Ellen O’Connell, “Unlawful Killing with Combat Drones: A Case Study of Pakistan, 2004–2009” in Simon Bronitt (ed.), Shooting to Kill: The Law Governing Lethal Force in Context (Hart Publishing, forthcoming); cites here are to the unpublished draft available online at <http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1501144> accessed November 4, 2011; Melzer, supra n.1.

⁶ Some studies that have examined the jus ad bellum aspects include; O’Connell, supra n.5; Norman G. Printer Jr, “The Use of Force Against Non-State Actors Under International Law: An Analysis of the U.S. Predator Strike in Yemen,” 8 UCLA Journal of International Law and Foreign Affairs (2003) 332; Jordan J. Paust, “Self-Defense Targetings of Non-State Actors and Permissibility of U.S. Use of Drones in Pakistan,” Journal of Transnational Law & Policy (2010) 237; Chris Jenks, “Law from Above: Unmanned Ariel Systems, the Use of Force, and Armed Conflict,” 85 North Dakota Law Review 649 (2009); and more broadly, Naom Lubell, Extraterritorial Use of Force Against Non-State Actors (Oxford University Press, 2010); Michael N. Schmitt, “Responding to Transnational Terrorism Under the Jus ad Bellum: A Normative Framework,” 56 Naval Law Review 1 (2008).

⁷ Harold Koh, speaking to the American Society of International Law, Washington, D.C., March 25, 2010 (transcript available online at <http://www.state.gov/s/l/releases/remarks/139119.htm> accessed November 4, 2011).

⁸ As several other chapters in this Volume describe in greater detail, there is little non-classified information on the criteria for targeting, the standards of proof required, or any other details of the process of selecting targets, final decision-making on issues of necessity and proportionality, and ex post review of the decision-making. For the extent to which the policy may come to extend to killing individuals for their “material support” of terrorists, see Section 7 of the draft legislation that was before the Armed Services Committee as this chapter was going to press: The Detainee Security Act of 2011, H.R. 968 I.H. (112th Congress 2011–12), available online at <http://thomas.loc.gov/cgi-bin/query/z?c112:H.R.968:> accessed November 4, 2011.

⁹ Koh, supra n. 7.

¹⁰ Speech of President George W. Bush, September 11, 2001, cited in Steven R. Ratner, “Jus ad Bellum and Jus in Bello After September 11,” 96 American Journal of International Law 905 (2002) 906.

¹¹ See text associated with infra nn. 103–05.

¹² I will below discuss some of the recent objections to the position taken here on those principles most central to the issue of targeted killing. This section begins with a sketch of the conventional understanding, as reflected in many leading works on the use of force and the decisions of the ICJ, as a baseline for discussion.

¹³ G.I.A.D. Draper, “Grotius’ Place in the Development of Legal Ideas About War” in Hedley Bull et al. (eds) Hugo Grotius and International Relations (Oxford University Press, 1990) 177–9; G.I.A.D. Draper, “The Origins of the Just War Tradition,” 46 New Blackfriars (2007) 82, 82–3; Stephen Neff, War and the Law of Nations: A General History (Cambridge University Press, 2005) chs 1 and 2.

¹⁴ Neff, supra n. 13, 49–53 Draper, supra n. 13, 180–3.

¹⁵ Neff, supra n. 13, 57–8, 102, and 176–8.

¹⁶ Ibid. at 59–61 and 126–9; also, on the writing of Gentili and Grotius on preventative and punitive war, see Richard Tuck, The Rights of War and Peace (Oxford University Press, 1999) 18–31 and 79–94; but see Larry May, Aggression and Crimes Against Peace (Cambridge University Press, 2008) 75–84.

¹⁷ Neff, supra n. 13, 97–102; and Tuck, supra n. 16, 102–06.

¹⁸ Neff, supra n. 13, 161–5, and ch 5. See also, generally, Tuck, supra n. 13; and Philip Bobbitt, The Shield of Achilles (Anchor Books, 2007) chs 8 and 21–3; and Yoram Dinstein, War, Aggression and Self-Defense, 4th edn (Cambridge University Press, 2005) ch. 3.

¹⁹ Dinstein, supra n. 18, 75–8 and 184–5; Neff, supra n. 13, ch. 6.

²⁰ For a history of these developments, see Neff, supra n. 13, chs 8–9; Brownlie, International Law and the Use of Force by States (Oxford University Press, 1963) chs 4–6; Dinstein, supra n. 18, ch. 4. For my own summary of these development of legal constraints on the use of force, see Craig Martin, “Taking War Seriously: A Model for Constitutional Constraints on the Use of Force in Compliance with International Law,” 76 Brooklyn Law Review 611 (2011) 633–61.

²¹ Art. 2(4) of the U.N. Charter.

²² U.N. Charter, arts 51 and 39–43, respectively. For an analysis of the modern jus ad bellum system, see e.g., Brownlie, supra n. 20, and Brownlie, “International Law and the Use of Force by States Revisited,” 21 Australian Year Book of International Law (2001); Dinstein, supra n. 18; Christine Gray, International Law and the Use of Force (Oxford University Press, 2008); Thomas M. Franck, Recourse to Force: State Action Against Threats and Armed Attacks (Cambridge University Press, 2002); Lindsey Moir, Reappraising the Resort to Force: International Law, Jus ad Bellum and the War on Terror (Hart Publishing, 2010); and Christopher Greenwood, Essays on War in International Law (Cameron May, 2006).

²³ Neff, supra n. 13, 279–80, 285–6, and 296–313. The Japanese invasion of Manchuria, characterized as an “incident,” and the Italian intervention in Ethiopia, were two of the primary examples of this failure of the League system.

²⁴ This issue will be examined in detail below: see infra nn. 80–87, and associated text.

²⁵ The mining of a naval vessel, and the firing of a silkworm missile at an ocean-going oil-tanker, for instance, were held not to constitute armed attacks for the purposes of triggering the right of self-defense. See in particular Oil Platforms (Iran v. U.S.), 42 I.L.M. 1334 (November 6, 2003), paras 51 and 64; see also Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. U.S.A.), (Merits Judgment), 1986 I.C.J. Reports 14, paras 191, 210–11, and 230–2.

²⁶ For further analysis and sources, see infra nn. 50–71 and associated text.

²⁷ Dinstein, supra n. 18, 237–42; Gray, supra n. 22, 148–55.

²⁸ Neff, supra n. 13, 326–34 (though tracing how states have tried to expand the concept since adoption of the U.N. Charter).

²⁹ Neff, supra n. 13, 111–14 and 186–9.

³⁰ On the IHL regime, see e.g. Yoram Dinstein, The Conduct of Hostilities Under the Law of International Armed Conflict (Cambridge University Press, 2004); Gary D. Solis, The Law of Armed Conflict: International Humanitarian Law in War (Cambridge University Press, 2010); Lindsay Moir, The Law of Internal Armed Conflict (Cambridge University Press, 2002); Anthony Cullen, The Concept of Non-International Armed Conflict in International Humanitarian Law (Cambridge University Press, 2010).

³¹ Jean-Marie Henckaerts and Louise Doswald-Beck (eds), Customary International Humanitarian Law, Vol. 2, (Cambridge: Cambridge University of Press, 2005) chs 1 and 2; Dinstein, supra n. 30, 27–8, 82–7; Solis, supra n. 30, 251–3;

³² Geneva Convention Relative to the Treatment of Prisoners of War, August 12, 1949, 75 UNTS (1950) 135, Art. 2, and Protocol Additional to the Geneva Conventions of August 12, 1949, and Relating to the Protection of Victims of International Armed Conflicts, (Protocol I), 1125 UNTS (1979) 3, Art. 1(3) and (4); See also Prosecutor v. Duško Tadiać, IT-94-1-A, July 15, 1999, (Appeals Chamber), para 84.

³³ Geneva Conventions, Common Art. 3; Protocol Additional to the Geneva Conventions of August 12, 1949, and Relating to the Protection of Victims of Non-International Armed Conflicts, (Protocol II), 1342 UNTS (1983) 137, Art. 1(1) (though note that the narrower definition in the Additional Protocol is not understood to constitute the minimum requirements for the existence of non-international armed conflict—see Melzer, supra n. 1, 256). 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, Protocol II is 1125 U.N.T.S. 609.

³⁴ See in particular Prosecutor v. Tadic, (Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction) October 2, 1995 (Jurisdiction Motion Appeal), paras 66–70; Prosecutor v. Tadic, Appeal Judgment, paras 83–96. See also Moir, supra n. 30, 489 et seq; and Melzer, supra n. 1, 252–61.

³⁵ Melzer, supra n. 1, 257–61; Marko Milanovic, “What Exactly Internationalizes an Internal Armed Conflict?,” EJIL Talk!, May 7, 2010, available online at <http://www.ejiltalk.org/what-exactly-internationalizes-an-internal-armed-conflict/> accessed November 4, 2011.

³⁶ Dinstein, supra n. 18, 156–68; Neff, supra n. 13, 340–6, 366–9; see also generally, Robert D. Sloane, “The Cost of Conflation: Preserving the Dualism of Jus ad Bellum and Jus in Bello in the Contemporary Law of War,” 34 Yale Journal of International Law 47 (2009); Alexander Orakhelashvili, “Overlap and Convergence: Jus ad Bellum and Jus in Bello,” 12 Journal of Conflict & Security Law 157 (2007); and Eyal Benvenisti, “Rethinking the Divide between Jus ad Bellum and Jus in Bello in Warfare Against Non-State Actors,” 34 Yale Journal of International Law 541 (2009).

³⁷ In fact, Sloane suggests that the independence of the regimes in the Charter era is actually exaggerated: Sloane, supra n. 36, 67–9.

³⁸ The “laws of war” is a term that is typically employed to describe the IHL regime alone, but I use it here to capture the overall system comprised of the two regimes.

³⁹ Dinstein, supra n. 18, 156–62 (also tracing how the evolution of jus ad bellum led to arguments in favor of re-integration of the regimes); Dinstein, supra n. 30, 14–16; Kretzmer, supra n. 1, 188; Melzer, supra n. 1, 247–51 and 394–5.

⁴⁰ Legality of the Threat or Use of Nuclear Weapons, ICJ Reports 1996, paras 75–87, and 95.

⁴¹ Ken Anderson has suggested that the self-defense claim can be grounded in domestic law arguments: Kenneth Anderson, “Targeted Killing in U.S. Counterterrorism Strategy and Law” in Benjamin Wittes (ed.), Legislating the War on Terror: An Agenda for Reform (Brookings Institution, 2009) 346, 347–8, 366–70.

⁴² Harold Koh stated that “the United States is in an armed conflict with Al Qaeda, as well as the Taliban and associated forces, in response to the horrific 9/11 attacks, and may use force consistent with its right to self-defense under international law.” This may be interpreted as two independent justifications, and the 9/11 attacks are linked specifically to the existence of an armed conflict, not the exercise of self-defense. See supra n. 9.

⁴³ But see Printer, supra n. 6, 352–8 (analyzing how self-defense is justified under jus ad bellum in a strike within Yemen, facilitated by the Yemeni government).

⁴⁴ O’Connell, supra n. 5, 16. And see infra nn. 51–71 and associated text.

⁴⁵ Ibid. at 16; Michael N. Schmitt, “Drone Attack Under the Jus ad Bellum and Jus in Bello: Clearing the ‘Fog of War’,” in Yearbook of International Humanitarian Law 2011 (Cambridge University Press, forthcoming) (cites to unpublished draft available online at <http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1801179> 4-5, accessed November 4, 2011.

⁴⁶ There has been considerable ambiguity over the extent to which the government of Pakistan has consented to or acquiesced in the targeted killing, which has also varied over the years. There can be little doubt that the Pakistani military, if not the government, has at various times consented to some of these strikes. At other times, such as following the killing of bin Laden, the government has quite clearly objected to them. See, e.g. O’Connell, supra n. 5, 16–18; David Sanger and Eric Schmitt, “As Rift Deepens, Kerry has Warning for Pakistan,” The New York Times, May 15, 2011, A16; and Greg Bruno, “U.S. Drone Activities in Pakistan,” Council on Foreign Relations Backgrounder, available online at <http://www.cfr.org/pakistan/us-drone-activities-pakistan/p22659#p6> accessed November 4, 2011. Similarly, there are questions regarding Yemen’s consent to strikes: Mark Mazzetti, “U.S. Intensifying a Secret Campaign of Yemen Airstrikes,” The New York Times, June 8, 2011; on occasion this has been explicitly with the cooperation of the Yemeni government: see Walter Pincus, “Missile Strike Carried Out with Yemeni Cooperation,” Washington Post, November 6, 2002, A10. Strikes in Somalia have occurred when there has been arguably insufficient central authority to provide consent. See Mark Mazzetti and Eric Schmitt, “U.S. Expands its Drone War Into Somalia,” The New York Times, July 2, 2011, A1.

⁴⁷ Consistent with this are the reports that the U.S. team that entered Pakistan for the purposes of killing bin Laden was prepared to use force against Pakistani forces if necessary; and reports that Pakistani authorities subsequently warned that it would use force against any such further violation of its sovereignty. See Eric Schmitt, et al. “U.S. Was Braced for Fight With Pakistanis in bin Laden Raid,” The New York Times, May 10, 2011, A1.

⁴⁸ See, e.g., Sean Murphy, “Terrorism and the Concept of ‘Armed Attack’ in Article 51 of the U.N. Charter,” 43 Harvard International Law Journal 41 (2002) 41–51; Dinstein, 207 supra n. 18; Lubell, supra n. 6, 33–4. For an extensive list of authorities supporting the proposition, see Paust, supra n. 7.

⁴⁹ Dinstein, supra n. 18, 202, citing Y.Z. Blum, “State Response to Acts of Terrorism,” 19 German Yearbook of International Law 223 (1976) 233; Tom Ruys, “Armed Attack” and Article 51 of the UN Charter: Evolutions in Customary Low and Practice (Cambridge: Cambridge University Press, 2010) 168–75; Gray, supra n. 22, 148; and Cassese, “The International Community’s ‘Legal’ Response to Terrorism,” 38 International and Comparative Law Quarterly (1989) 589, 596.

⁵⁰ See e.g., Gray, supra n. 22, 198–202; Dinstein, supra n. 18, 206–08; and Alston, supra n. 1, paras 40–1. Of course, there are many in the U.S. who reject this view. See, e.g. Paust, supra n. 6.

⁵¹ Art. 2(4) of the United Nations Charter.

⁵² See, e.g., Paust, supra n. 6. The Caroline incident involved a British attack in 1837 on a vessel being used by American sympathizers to supply a rebel force that had taken up arms against the British in Upper Canada. While Secretary of State Webster’s formulation of the right to self-defense in correspondence relating to the incident has come to comprise the seminal articulation of the principle, as Dinstein points out the incident took place at a time when there was no prohibition on the use of force, and was in essence about preventing a measure short of war leading to the outbreak of full-blown hostilities. See Dinstein, supra n. 18, 274–5.

⁵³ Brownlie, supra n. 20, ch. 13, and Brownlie, “Legal Regulation of the Use of Force,” 8 International and Comparative Law Quarterly (1959) 717–20. See also Dinstein, supra n. 18, 182–7. On the drafting history and interpretation of Art. 51, in addition to Brownlie, see e.g. Ruys, supra n. 49, 55–68; and Franck, supra n. 22, 45–50 (Kindle edition); also Nicholas Tsagourias, “Non-State Actors and the Use of Force” in J. d’Aspremont (ed.), Participants in the International Legal System: Multiple Perspectives on Non-State Actors in International Law (Routledge, 2011) 326, 328–9.

⁵⁴ On the overlap between art. 51 and customary international law, see Nicaragua v. U.S.A., supra n. 28, paras 172–82 and 187–201.

⁵⁵ See Gray, supra n. 22, 195; Lubell, supra n. 6, 29–31; and Ruys, supra n. 49, 369–485.

⁵⁶ See, e.g. Dinstein, supra n. 18, 245–51 (making a claim for such use of force as a form of extra-territorial law enforcement), and Lubell, supra n. 6, 36–7. The classic example cited is the use of force by Israel in Lebanon, against the PLO in 1982, and against Hezobllah in 2006.

⁵⁷ U.N. General Assembly Resolution 3314, (XXIX) (1974), Annex, art. 3(g).

⁵⁸ Nicaragua v. U.S.A., supra n. 25, paras 103; and 195. The dissenting judgments, particularly that of Judge Schwebel, disagreed strongly on the facts as to whether Nicaragua had been “substantially involved” in the operations of insurgents within El Salvador, and differed on where to draw the line between mere support and substantial involvement, but did not disagree with the principle. See opinion of Schwebel J., paras 154–71.

⁵⁹ Many scholars here discuss the court’s articulation of an “effective control” test, and contrast it to the ICTY “overall control” test in Tädic, but it is submitted that the effective control test was applied for the purposes of determining responsibility for violations of IHL, and not the use of force. See Nicaragua v. U.S.A., supra n. 25, paras 115 and 227.

⁶⁰ Case Concerning Armed Activities of the Territories of the Congo (Democratic Republic of the Congo v. Uganda) 2005 ICJ Reports 116, paras 132–3.

⁶¹ Ibid. paras 146–7. Though, in a cryptic paragraph ending this analysis, the court stated that it did not need to address the question of “whether and under what conditions contemporary international law provides for a right of self-defense against large-scale attacks by irregular forces.” Ibid. para 147.

⁶² For further discussion of factors that might be considered, see Lubell, supra n. 6, 36–8.

⁶³ Corfu Channel (United Kingdom v. Albania) (Merits), ICJ Reports (1949), 18–23.

⁶⁴ Dinstein, supra n. 18, 206.

⁶⁵ See, e.g. Dinstein, supra n. 18, 207; Christian J. Tams, “The Use of Force Against Terrorists,” 20 European Journal of International Law (2009) 359.

⁶⁶ U.N. Security Council Resolutions 1368, September 12, 2001, U.N. Doc. S/RES/1368 (2001); and Resolution 1373, September 28, 2001, U.N. Doc. S/RES/1373 (2001).

⁶⁷ The preambles of both resolutions recognize “the inherent right of individual or collective self-defence in accordance with the Charter,” while Res. 1368 condemned the terrorist attacks of 9/11 as a threat to peace and security; and Res. 1373 reaffirmed the duty of states to refrain from assisting or participating in terrorist acts against another state, and in its operable paragraphs also “decided” that states shall refrain from providing any such support. In short, the resolutions do not tie the acknowledgement of the right of self-defense to a use of force against terrorist groups per se, and they can indeed be interpreted as acknowledging the right of self-defense against states that are sufficiently responsible for supporting the terrorist activities leading to such attack. The ICJ interpreted these resolutions in this restrictive fashion in Advisory Opinion on the Security Wall in the Palestine Occupied Territories, para 139. See also, Gray, supra n. 22, 193–4, and 199; but see Dinstein, supra n. 18, 207; and Lubell, supra n. 6, 35.

⁶⁸ Gray, supra n. 22, 200.

⁶⁹ See Ruys, Article 51 of the UN Charter, supra n. 53, 486–7, on the nature of ambiguity.

⁷⁰ See ibid. at 199.

⁷¹ Ruys, Article 51 of the UN Charter, supra n. 53, 485–9. As Ratner puts it, “harboring” as articulated by the Bush administration at least means toleration, and that while the Bush doctrine on harboring may have been vague at the margins, it did not endorse the view that states “despite bona fide law enforcement, are unable to prevent or punish [terrorist actions], are harboring terrorists.” Ratner, supra n. 10, 907–08, and fn. 15. But see Tsagourias, supra n. 53, 328–9, and Schmitt, supra n. 46, 5.

⁷² Montevideo Convention on the Rights and Duties of States, 165 L.N.T.S. 19, signed December 26, 1933, art. 1.

⁷³ For a useful analysis of the structure of terrorist organizations and the extent to which they might be subject to the laws of war, see Matthew C. Waxman, “The Structure of Terrorism Threats and the Laws of War,” 20 Duke Journal of Comparative & International Law (2010) 429; on the nature of legal personality in international law, the seminal case is Reparation for Injuries Suffered in the Service of the United Nations, 1949 I.C.J. Reports 174.

⁷⁴ Cullen, supra n. 30, ch. 4; Melzer, supra n. 1, 254. Moir, supra n. 30, 489 (Kindle edition). Additional Protocol II to the Geneva Conventions, Art. 1(2).

⁷⁵ My thanks to Jens Ohlin for bringing this paradox into stark relief.

⁷⁶ This is akin to the analysis of the rights of self-defense, of both the potential victim and a bystander, against the “psychotic aggressor”—i.e., an aggressor who is morally blameless, but who is nonetheless intent on attacking the victim. See, George P. Fletcher and Jens David Ohlin, Defending Humanity: When Force is Justified and Why (Oxford University Press, 2008) 107–09. However, states are not, of course, monolithic entities, and so in some contexts the analogies to domestic criminal law can break down. Here we are not really talking about the choice of harm to one of two moral entities, but missile strikes that most often result in the killing of innocent civilians on the one hand, versus the possible future deaths of undetermined civilians in the defending state if the strike is not undertaken. The German Constitutional Court considered such a dilemma in a challenge to aerial security law authorizing the military to shoot down an airliner to prevent it being employed as a weapon. The court held that the law was unconstitutional, a violation of the right to life and guarantee of human dignity. Federal Constitutional Court, “Luftsicherheitsgesetz” Case, January 11, 2005, BVerfG, 1BvR 357/05; and see discussion of the case in Melzer, supra n. 1, 16–18.

⁷⁷ Ruys, Article 51 of the Charter, supra n. 53, 488–9.

⁷⁸ For an example of an individual strike approach, see e.g., Jenks, “Law from Above,” 85 North Dakota Law Review (2010) 659–60.

⁷⁹ For one thing, many of those targeted have been low-level operatives. Eric Schmitt, “New C.I.A. Drone Attack Draws Rebuke from Pakistan,” The New York Times, April 14, 2011, A10.

⁸⁰ Jenks, “Law from Above,” supra n. 78, 656–60. It should be noted that there is no well-established usage of these terms—some commentators distinguish between “anticipatory” and “preemptive,” others between “preemptive” (in a sense similar to “anticipatory,” or in response to imminent attack) and “preventative.” As Greenwood notes, therefore, some caution is necessary in interpreting the positions adopted by commentators: Greenwood, supra n. 22, 668. For a fuller analysis of this issue, see chapter 6 of this Volume, Claire Finkelstein, “Targeted Killing as Preemptive Action.” In this Volume, ch. 6.

⁸¹ The so-called Bush Doctrine, justifying the use of force to prevent the development of future threats, was formalized in the National Security Strategy for the United States, 2002.

⁸² See text associated with supra nn. 52–57.

⁸³ Gray, supra n. 22, 118 and 160; Ruys, Article 51 of the Charter, supra n. 53, ch. 5.

⁸⁴ Gray, supra n. 22, 160–6; Greenwood, Essays on War, supra n. 22, 675–6.

⁸⁵ The ICJ has continued to insist that an armed attack is a necessary pre-condition to the use of force in self-defense (though in Nicaragua it expressed “no view” on the validity of anticipating self-defense). See, e.g. Nicaragua v. U.S.A., supra n. 25, paras 194–95; Oil platforms, supra n. 25, paras 61–64: Congo v. Uganda, supra n.60, paras 143–47.

⁸⁶ Dinstein, supra n. 18, 185–91; Greenwood, supra n. 22, 672–5; Gray, supra n. 22, 117–19 and 160–6; and Lubell, supra n. 6, 55–7; see also, Peter Goldsmith, Attorney Gen., Testimony Before the U.K. Iraq Inquiry (January 27, 2010), available at <http://www.iraqinquiry.org.uk/transcripts/oralevidence-bydate/100127.aspx> accessed November 4, 2011.

⁸⁷ Caution has to be observed in distinguishing between arguments supporting “anticipatory self-defense,” and the much broader “preventative” use of force inherent to the Bush Doctrine. But rejecting the broad customary international law view, see, e.g., Brownlie, supra n. 22, 24–5; Dinstein, supra n. 18, 175–87 and 247–9; Gray, supra n. 22, 117–19 and 160–6; Franck, supra n. 22, ch. 7 (“defending a narrow conception of anticipatory self-defense”); Ruys, Article 51 of the charter, supra n. 53, 255–305 and 318–42; Greenwood, supra n. 22, 672–7 and 699; Printer, supra n. 6, 337–44. Contra, see e.g. Paust, supra n. 6, 238–49; and more broadly, William C. Bradford, “The Duty to Defend Them: A Natural Law Justification for the Bush Doctrine of Preventative War,” 79 Notre Dame L. Rev. 1365 (2004); Sean Murphy, “The Doctrine of Preemptive Self-Defense,” 50 Villanova Law Review (2005) 699. There are more philosophical normative works that explore why the right of self-defense ought to be broader than that allowed by art. 51: see e.g. Michael Walzer, Just and Unjust War, 3rd edn (Basic Books, 2000), and more recently, Fletcher and Ohlin, supra n. 76.

⁸⁸ Dinstein, supra n. 18, 236–7; Gray, supra n. 22, 193–4 (though acknowledging broader claims); Greenwood, supra n. 22, 424–5.

⁸⁹ Anderson, a strong advocate for the policy, recognizes this very problem in his argument that the U.S. needs to ground its justification in non-IHL principles: Anderson, supra n. 41, 357–8.

⁹⁰ For more on the nature of the various groups operating in the tribal areas of Western Pakistan, see Jayshree Bajoria, “Pakistan’s New Generation of Terrorists,” Council for Foreign Relations, available at <http://www.cfr.org/pakistan/pakistans-new-generation-terrorists/p15422#p1.> accessed November 4, 2011. John Rollins, “Al Qaeda and Affiliates: Historical Perspective, Global Presence, and Implications for U.S. Policy,” Congressional Research Service, January 25, 2011; and also, the FATA Research Center reports on drone attacks, available at <http://www.frc.com.pk/linkc/otherContent/6#4>.

⁹¹ Ken Dilanian, “CIA Plans Drone Campaign in Yemen,” Los Angeles Times, June 14, 2011.

⁹² See Jane Novak, “Arabian Peninsula al Qaeda Groups Merge,” The Long War Journal, January 26, 2009, available at: <http://www.longwarjournal.org/archives/2009/01/arabian_peninsula_al.php> accessed November 4, 2011; and Alistair Harris, “Exploiting Grievances: Al Qaeda in the Arabian Peninsula,” A Carnegie Paper Series, No. 111, May 2010.

⁹³ Greg Jaffe and Karen de Young, “U.S. Drone Targets Two Leaders of Somali Group Allied With Al Qaeda, Official Says,” The Washington Post, June 29, 2011.

⁹⁴ Yet many scholars tend to characterize the strikes in Yemen as being a response to 9/11. See, e.g., Printer, supra n. 6, 352–5.

⁹⁵ Harris, supra n. 92, 4.

⁹⁶ Moreover, the intention is to extend this general right of self-defense to any group that the U.S. determines to be “hostile.” See supra n. 8.

⁹⁷ The ICJ has held, for instance, that the U.S. destruction of Iranian oil platforms in response to the mining of an American frigate was neither necessary nor proportionate, and thus not a justifiable use of force under the self-defense exception. Oil Platforms Case, para. 77.

⁹⁸ Walter Pincus, “Missile Strike Carried Out with Yemeni Cooperation,” Washington Post, November 6, 2002, A10.

⁹⁹ Melzer, supra n. 1, ch. 2. An increasing number of countries are reported to be developing military drone capabilities: see Jenks, “Law from Above,” supra n. 78, 654.

¹⁰⁰ See Dinstein for this argument in support of limited use of force against terrorists operating within the territory of another state: Dinstein, supra n. 18, 244–7.

¹⁰¹ See Kenneth Anderson, Written Testimony to U.S. House of Representatives Committee on Oversight and Government Reform, Subcommittee on National Security and Foreign Policy, Subcommittee Hearing “Drones II,” April 26, 2010; and Subcommittee Hearing “Rise of the Drones: Unmanned Systems and the Future of War,” March 18, 2010.

¹⁰² Anderson, supra n. 41, 347–8 and 356–7.

¹⁰³ See supra n. 35.

¹⁰⁴ As this Volume was going to press, evidence emerged that there continues to be a debate within the government on the relationship between the two justifications: Charlie Savage, “At White House, Weighing the Limits of Terror Fight” The New York Times, September 16, 2011, A1; and Marty Lederman, “John Brennan Speech on Obama Administration Antiterrorism Policies and Practices,” Opinio Juris, September 16, 2011, available at <http://opiniojuris.org/2011/09/16/john-brennan-speech-on-obama-administration-antiterrorism-policies-and-practices/> accessed November 4, 2011. To his credit, Ken Anderson has, in his testimony before Congress and his scholarship, argued that the U.S. government ought to develop and clearly articulate a much more detailed legal justification for its policy in this area. See supra nn. 100–101.

¹⁰⁵ Anderson also interprets U.S. policy as being based on alternative arguments. Anderson, supra n. 41, 365–6; as does the Pentagon: Charlie Savage, “At White House, Weighing the Limits of Terror Fight,” The New York Times, September 16, 2011, A1.

¹⁰⁶ This propensity is similarly seen in the detention and military commission policies.

¹⁰⁷ See supra n. 38.

¹⁰⁸ On the debate leading to these “decisions,” see Neff, supra n. 13, 335–40.

¹⁰⁹ See the Correlates of War Project—J. David Singer and Melvin Small, Resort to Arms: International and Civil Wars, 1816–1980, 2nd edn (Sage, 1982).

¹¹⁰ Jeremy Waldron, “In Justifying Targeted Killing with a Neutral Principle?,” in this Volume, ch. 4.