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Eric Allen Engle, Targeted Killing? Terrorists, Insurgents, and Pirates, Berkeley Journal of International Law, Publicist, #9, '11 (2011). 

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'On November 3, 2002, a U.S. Predator unmanned aerial vehicle launched a missile at a car traveling in a remote part of Yemen, killing six men, all suspected members of the Al Qaeda terrorist network. . . Since 2002, the United States has continued to employ the same tactic used in the al-Harithi attack in its 'Global War on Terror.''2 Such attacks are a timely topic and have been examined in depth by other scholars.3 In this brief article I wish to point out two lacunae in international law: an absent definition of the term 'terrorist' and a similarly inchoate definition of 'assassination' (sometimes referred to as 'targeted killing'4). These lacunae create a legal uncertainty: may states assassinate 'terrorists'? If so, under what conditions?

I suggest a solution to the lacunae. Unlike terrorism, piracy and insurgency are well defined under international law. We can analogize terrorists to pirates and insurgents to understand the legal rights and duties of States. I argue that, as a general rule, 'terrorism' is analogical to piracy and, accordingly, is not governed by the law of war.5 Instead, 'terrorism', like piracy,6 is subject to national and/or conventional international criminal law, prohibits extrajudicial killing.7 Prior to former President Bush's lawless 'global war on terror' terrorism was clearly seen as a criminal act and had not been considered an act of war. As an exception to that general rule, taking into account the actual state practice of the last lawless decade, some terrorism could be seen as analogical to insurgency in zones of armed conflict8 and could therefore be subject to the law of war,9 which may displace the ordinary criminal law regime.10 State practice is one element of international customary law. Prior to September 11, state practice universally regarded war as an armed conflict between states. International lawyers can hardly be asked to ignore what states in fact actually do when describing the other element of international customary law ' the opinio juris of what states ought to do.

Assassination, which is per se illegal outside of a zone of armed conflict, is presumed illegal during an armed conflict. However, that presumption might be rebuttable. During an armed conflict, and only then, using deadly force against terrorists directly engaged in combat may be justified, if, and only if, such killing was a necessary11 and proportional12 act of self defense13 in a zone of armed conflict.

Terrorism ' Undefined under International Law

There is no generally accepted definition of 'terrorist' under customary international law.14 Terrorism remains undefined under customary international law15 because of the political nature of the crime. However, several international conventions address particular aspects of terrorism,16 and often provide for universal jurisdiction.17 Because terrorism is undefined, we should analogize terrorism to piracy and insurgency, both of which are well defined, to determine the legal rights and duties of states with regard to 'terrorists'/'freedom fighters.' Terrorists, like insurgents and pirates, are non-state actors18 exercising violence internationally against a state power or powers, creating thereby an issue of mutual and not merely several concern to states19 in their relationships to each other; and thus concern the international system as a whole, and not merely each state separately. Because the threat posed by terrorists is sometimes a threat to the international system as a whole, such terrorist activities are subject to international law - unlike purely local and internal issues, which are in contrast subject only to national law. By analogizing terrorism to piracy or insurgency we can thereby determine whether and when (international criminal law applies (the general rule) or instead the law of war applies (the exception) or domestic law.


Historically, war ('international armed conflict') has been defined as being exclusively the prerogative of States. Under this definition, a state of war cannot exist between a State and a non-State actor.20The 'global war on terror' is thus a misnomer because, in addition to the historical definition of war, public international law, as a general rule, governs the relationships of States, only, in their mutual relations.21 As an exception to that general rule, public international law accords directly enforceable rights and duties to private persons,22 as in the case of jus cogens23 and via treaties intended to have direct effect. States are presumed to be the sole addressees of public international law. Exceptions to that general rule certainly exist, but the exceptions must be proven by whoever asserts them due to the general principle of law that onus probandi actori incumbit.24

In at least one instance, however, the law of armed conflict applies to a class of non-state actors: insurgents.25 Insurgents can be regarded properly as a belligerent party26 subject to the laws of war and accorded rights and duties under international humanitarian law27 as participants in hostilities28 per the Second Additional Protocol to the Geneva Conventions.29 Although many states are not party to this treaty, the principle that non-State actors have rights and duties during armed conflict is a general proposition of customary international law.30 Insurgents, unlike terrorists, are not subject to universal jurisdiction due to their status.31


Pirates and terrorists are considered to be hostes humanis generis - enemies of all mankind.32 Because of such status, pirates33 (as a matter of customary law) and terrorists (as a matter of international conventions, i.e. multi-lateral treaties)34 are subject to universal jurisdiction. As a general rule, terrorists are not subject to universal jurisdiction; the international conventions that create universal jurisdiction over certain terrorist acts are exceptions to the general presumption against universal jurisdiction.

Unlike insurgents, pirates have never been considered armed combatants owed duties and enjoying rights under the laws of war, even though privateers, granted letters of marque by States, acted much like pirates.35 Likewise, terrorists have not historically been considered armed combatants subject to the law of war. One can recall the experiences of Britain and the I.R.A.,36 of France and Spain as to the E.T.A. and of Germany with the R.A.F.,37 as well as those of Italy and Japan with the Red Brigades. None of those instances of severe terrorism were treated as armed conflicts. These commonalities between terrorists and pirates lead me to conclude that terrorists are more like pirates than insurgents, as shown by the numerous international treaties criminalizing various aspects of terrorism - and the absence of international conventions casting terrorists into the role of belligerents to an armed conflict. Terrorists are thus presumed to be subject first to national criminal law (the general rule), then, exceptionally, to international criminal law via specific universal jurisdiction conventions (not customary international law), and finally, as another exception to the general rule, to international humanitarian law, i.e. the law of war, in zones of armed conflict, whether national (insurgency) or international (war).

The Use of Force in International Law

Assassination: Undefined under International Law

Like 'terrorism,' 'assassination' is undefined in international law.38 That fact makes legal analysis of assassination, especially in the context of terrorism, difficult or even impossible, and adds to the controversy and legal uncertainty regarding assassination of terrorists. To understand the legal definition of the term assassination, we must look to how it has been used historically.

Assassination as a legal issue first appeared in the context of tyrannicide.39 Ancient scholars such as Aristotle and Cicero40 considered tyrannicide a natural right of an oppressed people against an unjust ruler.41 In contrast, medieval and early modern scholars, such as Aquinas42 and Grotius,43 regarded assassination in war by an enemy power through treachery as unlawful.44 Late modernity continued that trend by outlawing the use of assassination entirely, ironically enough, because terrorists used the tactic of assassinations.45 Unsurprisingly, assassination is illegal under U.S.46 and international law.47 Notwithstanding its illegality under international law, some argue for an emerging right to commit assassinations, at least during armed conflicts.48 This argument is based on the ability of States to use force in self- defense, which can then justify an otherwise unlawful use of force.49 However, the use of force in international law must be proportional to the threat and necessary.50 Consequently, we now turn to a proportionality analysis to understand the legal status of assassination.

Proportionality of the Use of Force

Advocates of assassination tend to distinguish the use of assassination in peace, where it is generally regarded'and rightly so' as per se unjustifiable, from its use during armed conflicts, where it might be justifiable in self-defense, subject to the general principle of proportionality in the use of force under international law.51 The proportionality principle requires that the use of force must be proportional to the threat it seeks to extinguish.52 The influential Swiss philosopher and international jurist Emerich De Vattel provides the proper context to understand the use of force in war: 'Nations are bound mutually to promote the society of the human race, [thus] they owe one another all the duties which the safety and welfare of that society require.'53 Consequently, force should only be used to reduce the use of force, and must be proportional to the threat. Assassination purportedly kills the right people and fewer civilians. If that were true, assassination might better meet the test of proportionality than other acts of war ' presuming it would not in turn unleash reprisal attacks ('blowback').

The Israeli Supreme Court is one of the few courts to have directly adjudicated the issue of the legality of assassination.54 So, we now look to the Israeli Supreme Court's analysis of the issues to find possible insights into this problem.

The Israeli Supreme Court

Admitted Israeli assassinations have killed approximately 300 intended persons and 150 innocent victims as well as wounding hundreds of other persons.55 The Israeli Court regards the Intifada as an international armed conflict.56 That, incidentally, is an act of de facto (not de jure) recognition of a Palestinian state, as is the ongoing Israeli negotiations with the Palestinian Authority toward mutual recognition and peaceful co-existence. As a logical consequence, the Israeli High Court regards the insurgents struggling for state power in the occupied territories as subject to the law of war.57 Applying the law of armed conflict to the Intifadah, the Israeli Court ruled that terrorists are civilians under the law of armed conflict.58 As such, they may only be attacked when directly participating in hostilities, and then only when such attacks are proportional and necessary.59 However, the Israeli Supreme Court broadened the definition of direct participation to cover bomb manufacturing and ancillary activities to armed conflict.60 Although international humanitarian law only recognizes two classes of persons in conflict zones'civilians and combatants' combatants who wear no uniform or distinctive identification61 are considered to be acting unlawfully. This distinction led the Israeli court to refer to such persons as 'unlawful combatants.'62 To the Israeli court, civilians indirectly engaged in armed combat in a conflict zone may be fairly attacked ' and that is by definition thus true as a matter of Israeli law' however, that goes beyond what international law permits: civilians must be directly engaged in combat to be legally targeted in conflict zones under public international law.


Comparing 'terrorists' to pirates and insurgents is useful because customary international law still has not defined the term 'terrorist.' Thus, the analogy provides some insight into understanding when and whether terrorists are subject to criminal law (either national or international), which is usually the case, or to the laws of war. As a general rule, terrorists are presumed to be subject to criminal law, not the law of war. Exceptionally, when directly participating in combat in a zone of armed conflict, terrorists may be combatants, subject to the law of war. Terrorists are generally more like pirates than insurgents because 1) they are subject to universal jurisdiction via international convention and in actual state practice, 2) they usually operate outside of zones of armed conflict, 3) they often seek their own private benefit (e.g., narco-terrorists, bank robbers), and 4) they do not always contend for state power and are presumptively not governed by public international law because state actors are the principle subjects of public international law. However, terrorists at some times and places will be combatants operating in a zone of armed conflict during an armed conflict and thus will be subject to the laws of war in such circumstances.

In the end, the idea of a 'war on terror' distorted the rule of law and wrought injustice. Casting the struggle against lawless violence as a 'war on terror' lent legitimacy to terrorists and belligerent rights that they otherwise did not have. Additionally, it created a vast gray area for abuse of the law through acts of torture, kidnapping, and assassination'including that of at least one U.S. citizen', while justifying endless wars with no clear goals in a spiral of violence. The war on t^error failed as a metaphor and legal concept: the way out is to understand that terrorists are criminals, not soldiers, and should be prosecuted accordingly.

1 Adjunct Lecturer, Humboldt University Berlin, Germany. For the nameless stars in heaven.

2 W. Jason Fisher, Targeted Killing, Norms, And International Law, 45 Colum. J. Transnat'l L. 711, 711 (2007).

3 See, e.g., Norman G. Printer, The Use of Force Against Non-State Actors Under International Law: An Analysis of the U.S. Predator Strike in Yemen, 8 UCLA J. Int'l L. & Foreign Aff. 331 (2003).

4 "A targeted killing is the intentional, premeditated and deliberate use of lethal force, by States or their agents acting under colour of law, or by an organized armed group in armed conflict, against a specific individual who is not in the physical custody of the perpetrator. . . Although in most circumstances targeted killings violate the right to life, in the exceptional circumstance of armed conflict, they may be legal. This is in contrast to other terms with which 'targeted killing' has sometimes been interchangeably used, such as 'extrajudicial execution', 'summary execution', and 'assassination', all of which are, by definition, illegal." U.N. Human Rights Council, Report of the Special Rapporteur on Extrajudicial, Summary or Arbitrary Executions, Addendum: Study on Targeted Killings, paras. 1, 10, U.N. Doc. A/HRC/14/24/Add.6 (May 28, 2010) (prepared by Philip Alston).

5 See, e.g., David Kretzmer, Targeted Killing of Suspected Terrorists: Extra-Judicial Executions or Legitimate Means of Defence? 16 Eur. J. Int'l L. 171, 201 (2005).

6 See Michael H. Passman, Protections Afforded to Captured Pirates Under the Law of War and International Law, 33 Tul. Mar. L. J. 1 (2008).

7 See International Covenant on Civil and Political Rights, art. 6, Dec. 16, 1966, 999 U.N.T.S. 171; Universal Declaration of Human Rights, G.A. res. 217A (III), U.N. Doc A/810 (1948); Peter Henner, Human Rights and the Alien Tort Statute: Law, History, and Analysis 128 (2009); Mary Ellen O'Connell, The Power and Purpose of International Law 9 (2008); Chandra Lekha Sriram, Olga Martin-Ortega & Johanna Herman, War, Conflict and Human Rights: Theory and Practice 146 (2010).

8 "An armed conflict which takes place between an Occupying Power and rebel or insurgent groups ' whether or not they are terrorist in character ' in an occupied territory, amounts to an international armed conflict" A. Cassese, International Law 420 (2d ed. 2005). For the definition of international armed conflict see, e.g., O. Ben-Naftali & Y. Shani, Hamishpat Habeinleumi Bein Milchama Le'shalom International Law Between War And Peace 42 (2006) []; Y. Dinstein, War, Aggression and Self-Defence 201 (4th ed. 2005); H. Duffy, The 'War On Terror' And The Framework Of International Law 219 (2005).

9 The law of war consists of jus ad bellum (the right to make war) and jus in bello (rights during war). International Humanitarian Law [hereinafter IHL] is jus in bello. IHL governs armed conflicts. However, lacunae in IHL can be supplemented by international human rights law. See Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, ICJ Reports 1996, 226, 240; Advisory Opinion on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, ICJ Reports 2004, 136; Bankovic v. Belgium, 41 ILM 517 (ECHR, 12 December 2001). See generally Theodor Meron, The Humanization of Humanitarian Law, 94 Am. J. Int'l L. 239 (2000).

10 "Petitioners note that a civilian participating in combat might lose part of the protections granted to civilians at a time of combat; but that is so only when such a person takes a direct part in combat, and only for such time as that direct participation continues. Those conditions are determined in article 51(3) of Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977." HCJ 769/02 Pub. Comm. Against Torture in Isr. v. Gov't of Isr. (PCATI) [Dec. 11, 2005 slip op. para. 6, available at

11 U.N. Secretary-General, Extrajudicial, Summary, or Arbitrary Executions, paras. 33-45, U.N. Doc. A/61/311 (Sep. 5, 2006); U.N. Human Rights Committee, General Comment No. 6, HRI/GEN/1/Rev.6, para. 3(1982); Inter-American Commission of Human Rights, Report on Terrorism and Human Rights, OEA/Ser.L/V/II.116, Doc. 5 rev. 1 corr. (2002).

12 See supra note 11.

13 Legality of the Use by a State of Nuclear Weapons in Armed Conflict, 1995 I.C.J. 25, para. 5 (Nov. 3) (Higgings, J., dissenting).

14 See, e.g., Ben Saul, Defining Terrrorism in International Law 5, 8 (2008).

15 See supra note 14, at 57, 191.

16 The various binding international conventions focus on specific acts such as, for examples, hijacking of aircraft and hostage taking, safeguarding. For a list, see Shirley V. Scott et al., International Law and the Use of Force 217-28 (2010).

17 Anthony Aust, Handbook of International Law 270 (2010). Although the conventions do provide for universal or extraterritorial jurisdiction, as a matter of customary international law it is 'premature to claim universal jurisdiction over terrorism, given the absence of an agreed definition, though its exercise might not give rise to protest.' Supra note 14, at 250.

18 Even where terrorism is state sponsored or state sanctioned terrorism the terrorist acts are usually committed by private persons.

19 Filartiga v. Pena Irala 630 F.2d 876, 888 (2d Cir. 1980).

20 See, e.g., L.F.L. Oppenheim, International Law: A Treatise 202 (H. Lauterpacht ed., 7th ed. 1952) (war is a "contention between two or more States through their armed forces"). The general consensus is that war can only exist between states; however, insurgents are accorded rights and duties under the law of armed conflict. See generally Daniel Pickard, When Does Crime Become a Threat to International Peace and Security, 12 Fla. J. Int'l L. 1 (1998).

21 Joseph Gabriel Starke, An Introduction to International Law 53 (1963).

22 Roland Portmann, Legal Personality in International Law 280 (2010).

23 A jus cogens norm "is a norm accepted and recognized by the international community of states as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character." See Siderman de Blake v. Republic of Argentina, 965 F.2d 699, 714 (9th Cir. 1992) (quoting Vienna Convention on the Law of Treaties, art. 53, May 23, 1969, 1155 U.N.T.S. 332, 8 I.L.M. 679).

24 See, e.g., Juliane Kokott, The Burden of Proof in Comparative and International Human Rights Law 184 (1998).

25 Leslie C. Green, The Contemporary Law of armed Conflict 58 (1993).

26 Prize Cases, 67 U.S.635, 644, 657 (1863).

27 International humanitarian or international human rights law can apply to armed conflicts which are not international, i.e. to domestic insurgencies. See Hamdan v. Rumsfeld, 548 U.S. 557 (2006); Prosecutor v. Tadic, Case No. IT-94-­1, para. 559, 655 (Int'l Crim. Trib. for the Former Yugoslavia, May 7, 1997), available at; supra note 5, at 194 (2000).

28 See, e.g., Cassese, supra note 8, at 66.

29 Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of Non-International Armed Conflicts [Protocol II], June 8, 1977, 1125 U.N.T.S. 609, available at

30 See HCJ 769/02 Pub. Comm. Against Torture in Isr. v. Gov't of Isr. (PCATI) [Dec. 11, 2005 slip op. para. 19, available at http:// See also supra note 29, para. 20.

31 See John O'Brien, International Law 246 (2001).

32 See, e.g., U.S. v. Smith, 18 U.S. 153 (1820).

33 Stephen Macedo, Universal Jurisdiction: National Courts And the Prosecution of Serious Crimes Under International Law 47 (2004).

34 See, e.g., Convention for the Suppression of Unlawful Seizure of Aircraft [Hijacking Convention], Dec. 16, 1970, 10 I.L.M. 133, 860 U.N.T.S. 105. For a list of the various treaties which the Hague Air Hijacking Convention inspired, see Adam Boczek Boleslaw, International Law: A Dictionary 83 (2005).

35 See Christopher Tomlins, Freedom Bound: Law, Labor, and Civic Identity in Colonizing English America 129 (2010); Hugo Grotius, On The Law Of War And Peace 154 (Kessinger Reprint, 2004) ("Pirates and robbers, as they form no civil community, cannot rest any claim to protection and support upon the law of nations.").

36 See, e.g., Lawless v. Ireland (No.3), 3 Eur. Ct. H.R. (ser. A) (1961); Ireland v. United Kingdom, 25 Eur. Ct. H.R. (ser. A) (1978).

37 See, e.g., BVerfGE 45, 434 - RAF (German Constitutional Court - Bundesverfassungsgericht); Gerhard Werle, Die Beteiligung an kriminellen Vereinigungen und das Problem der Klammerwirkung, Juristische Rundschau. Volume 1979, Issue 3, Pages 93'99. See generally, Ausgewählte Dokumente der Zeitgeschichte: Bundesrepublik Deutschland (BRD) - Rote Armee Fraktion (RAF), GNN Verlagsgesellschaft Politische Berichte, (1st edn. Köln, Oktober 1987). Note, however, that Professor Axel Azzola argued that the RAF should be treated as prisoners of war. See generally, OlG Stuttgart 2 StE 1/74. (State Appellate Court- Oberlandsgericht, Stuttgart, 1974 - Stammheimer Trial); Uwe Schultz, Grosse Prozesse: Recht und Gerechtigkeit in der Geschichte, 421 (Beck, 2001).

38 Matthew C. Wiebe, Assassination in Domestic and International Law: The Central Intelligence Agency, State-Sponsored Terrorism, and the Right of Self-Defense, 11 Tulsa J. Comp. & Int'l L. 363, 365 (2003).

39 Louis Rene Beres, Assassinating Saddam Hussein: The View from International Law, 13 Ind. Int'l & Comp. L. Rev. 847, 847 (2003).

40 See Marcus Cicero, De Officiis, in The Terrorism Reader: A Historical Anthology 16 (Walter Lacquer ed., 1978).

41 See Lacquer, supra note 40, at 7-43.

42 Thomas C. Wingfield, Taking Aim at Regime Elites: Assassination, Tyrannicide, and the Clancy Doctrine, 22 Md. J. Int'l L. & Trade 287, 295 (1998).

43 See Hugo Grotius, The Law of War and Peace, in 1 Law of War: A Documentary History 16 (Leon Friedman ed., 1972).

44 David Ennis, Preemption, Assassination, and the War on Terrorism, 27 Campbell L. Rev. 253, 255 (2005).

45 See supra note 39, 853-54.

46 See U.S. Const. amend. V ('No person shall be ' be deprived of life, liberty, or property, without due process of law.'); U.S. Const., amend. VI ('[T]he accused shall enjoy the right to a speedy and public trial, by an impartial jury.'). United States Intelligence Activities, Exec. Order 12333, 3 C.F.R. 1981, Section 2.11 (Dec. 4, 1981) ("No person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination.").

47 Howard A. Wachtel, Targeting Osama Bin Laden: Examining the Legality of Assassination as a Tool of U.S. Foreign Policy, 55 Duke L.J. 677, 677 (2005).

48 See supra note 2 (arguing that assassination is currently illegal lex lata, but is de lege ferenda state practice).

49 W. Hays Parks, Memorandum of Law: Executive Order 12,333 and Assassination, 1989 Army Law. 4, 7 (1989), available at (arguing that assassination can be a justifiable use of force in self-defense).

50 Malcolm Nathan Shaw, International Law 1031 (2003).

51 See supra note 10, at para. 41.

52 Myra Williamson, Terrorism, War and International Law: the Legality of the Use of Force Against Afghanistan in 2001 115 (2009).

53 See 3 Emmerich De Vattel, The Law of Nations or the Principles of Natural Law xii (George D. Gregory trans., 1916) (1758).

54 See supra note 10, para. 2.

55 Kristen E. Eichensehr, On Target? The Israeli Supreme Court and the Expansion of Targeted Killings, 116 Yale L.J. 1873, 1873 (2007).

56 See PCATI, supra note 10, at para. 16.

57 See PCATI, supra note 10, at para. 18.

58 See PCATI, supra note 10, at para. 25.

59 See PCATI, supra note 10, at para. 34.

60 See PCATI, supra note 10, at para. 2.

61 See PCATI, supra note 10, at para. 2 (Rivlin, concurring).

62 See Yoram Dinstein, The Conduct of Hostilities Under the Law of International Armed Conflict 29-30 (2004).