1 I work with the assumption that since September 11,2001, the United States and Al Qaeda have been engaged in an armed conflict that is regulated in part by international humanitarian law—a proposition that all three branches of the U.S. government have accepted. See, e.g., Hamdan v. Rumsfeld, 548 U.S. 557, 630–31 (2006); Military Commissions Act of 2006, Pub. L. No. 109–366,120 Stat. 2600 (codified at 10 U.S.C. §§948a–950w and other sections of titles 10, 18, 28, and 42 (2006)); Deputy Secretary of Defense Gordon England, Memorandum for Secretaries of the Military Departments et al. (July 7, 2006), available at < ; cf. Exec. Order, Ensuring Lawful Interrogations (Jan. 22, 2009), available at <.

Accepting the existence of an armed conflict for the purpose of this analysis is not meant to express any view on the merits of the war model versus the criminal law model. The existence of an armed conflict would not preclude the Obama administration from confronting the Qaeda threat through the criminal justice system and ordinary administrative measures rather than instruments of war. The administration might also take steps to alter the situation so that it is no longer classifiable as an armed conflict. Indeed, many of the indicia of an armed conflict in the present situation are the result of military and diplomatic actions adopted by the U.S. government after September 11. See Jinks, Derek September 11 and the Laws of War , 28 Yale J. Int’l L. 1 (2003).Google Scholar Some of those actions could be revised if not reversed. I take no position on those policy choices, which are beyond the scope of this essay. For so long as the situation remains an armed conflict with Al Qaeda—whether in Afghanistan, Iraq, or globally —the present analysis of the IHL regime is relevant.

2 Some of these errors may have understandably resulted from trepidation about approving the preventive detention of civilians, from the perceived novelty of a conflict with a transnational armed group, or from insufficient expertise in IHL. I am agnostic as to which (combination) of these or other reasons led to distorted representations of existing law.

3 See infra text at notes 65–75.

4 See infra text at notes 78–86.

5 See infra text at notes 87–100.

6 Al–Marri v. Pucciarelli, 534 F.3d 213 (4th Cir. 2008) (en banc), cert, granted, 11 U.S.L.W. 3148 (U.S. Dec. 5, 2008) (No. 08–368).

7 Goodman, Ryan & Jinks, Derek International Law, U.S. War Powers, and the Global War on Terror , 118 Harv. L. Rev. 2653, 2659–61 (2005)Google Scholar. For example, detainees in all armed conflicts are at least protected by die fundamental humanitarian requirements of common Article 3. See, e.g., Convention Relative to the Protection of Civilian Persons in Time of War, Art. 3, Aug. 12, 1949, 6 UST 3516, 75 UNTS 135 [hereinafter Fourth Geneva Convention].

8 Common Article 3 refers to “active” participation. See infra note 18 (discussing lack of difference between “active” and “direct” participation).

9 The proposition here relates only to IHL. The application of other legal regimes—e.g., human rights law— might complicate this account, especially insofar as those rules impose obligations on the exercise of state power domestically and not extraterritorially.

10 Related to this proposition is another axiom of the legal regime: IHL prohibitions that apply in noninternational armed conflict (e.g., common Article 3) a fortiori apply in international armed conflict. See Brief of Amici Curiae Professors Ryan Goodman, Derek Jinks & Anne-Marie Slaughter at 24–25, Hamdan v. Rumsfeld, 548 U.S. 557 (2006) (No. 05–184).

11 Some commentators suggest, as an answer to this point, that domestic law, rather than IHL, provides the legal basis for detention of civilians in noninternational armed conflict. See, e.g., Rona, Gabor An Appraisal of US Practice Relating to ‘Enemy Combatants,’ 2007 Y.B. Int’l Humanitarian L. 232, 240–41, available at <Google Scholar. Note, however, that that claim is analytically the same as the original point. Both of them contend that IHL does not constrain states’ detention power and that states are thus free to act in accordance with their own national law and policy choices.

12 See infra note 23; see also Dingwall, Joanna Unlawful Confinement as a War Crime: The Jurisprudence of the Yugoslav Tribunal and the Common Core of International Humanitarian Law Applicable to Contemporary Armed Conflicts , 9 J. Conflict & Security L. 133, 144 (2004)Google Scholar (analyzing jurisprudence of the International Criminal Tribunal for the Former Yugoslavia (ICTY) in support of rule that “confinement of civilians in internal armed conflict is unlawful when civilians are detained without reasonable grounds to believe that the security of the Detaining Power makes it absolutely necessary”); Zegveld, Liesbeth The Accountability of Armed Opposition Groups in International Law 65–66 (2002)Google Scholar (discussing examples from UN Commission on Human Rights); Inter–Am. Comm’n on Human Rights, Third Special Report on the Human Rights Situation in Colombia, OEA/Ser.L/V/II.102, doc. 9, rev.1 (Feb. 26, 1999) (applying prohibition in Colombian civil war); cf. 1 International Committee of the Red Cross [ICRC], Customary International Humanitarian Law 344, 347–49 (Jean–Marie, Henckaerts & Louise, Doswald–Beck eds., 2005).Google Scholar

13 Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of International Armed Conflicts, Art. 51(3), June 8, 1977, 1125UNTS3 [hereinafter Protocol I]; Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of Noninternational Armed Conflicts, Art. 13(3), June 8, 1977, 1125 UNTS 609 [hereinafter Protocol II].

14 Knut, Dörmann The Legal Situation of “ Unlawful/Unprivileged Combatants!’ 85 Int’l Rev. Red Cross 45, 46 (2003)Google Scholar (“The terms ‘unlawful combatant’, ‘unprivileged combatant/belligerent’.... have, however, been frequently used at least since the beginning of the last century in legal literature, military manuals and case law.”); Roberts, Adam Remarks, in Counterterrorism and the Laws of War: A Critique of the U.S. Approach (discussion at the Brookings Institution, Mar. 11, 2002), available at <Google Scholar (“There is a long record of certain people coming into the category of unlawful combatants—pirates, spies, saboteurs, and so on. It has been absurd that there should have been a debate about whether or not that category exists.”).

15 Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 Google Scholar, Commentary on Protocol I, Art. 51(3), at 619 (Yves Sandoz, Christophe Swinarski, & Bruno Zimmermann eds., 1987).

16 Id., Commentary on Protocol I, Art. 43, at 516.

17 Id., Commentary on Protocol II, Art. 13, at 1453. W. Hays Parks—the leading proponent of a broad standard for participation—argues that customary international law supports a more expansive definition that would preclude civilians from providing functionally important, though less immediate, support to the military effort. The hypothetical that Colonel Parks uses to illustrate how his approach differs from the Protocol approach is “ [a] civilian… driving a military truck filled with ammunition towards his front lines.” W. Hays, Parks Air War and the Law of War , 32 A.F. L. Rev. 1, 134 (1990).Google Scholar That this is considered a hard case illustrates the substantial agreement between the two camps. Even on Colonel Parks’s view, civilians are not precluded from participating in “logistics support,” “national C3I [command, control, communications, and intelligence],” “war manufacturing,” “defense R&D,” or other war–related efforts. Id. at 122 fig. 1.

18 There is some technical disagreement over whether the level of participation required is best characterized as “direct” or “active.” See, e.g., U.S. Army, Senior Officer Legal Orientation Deskbook 43–8 to 43–14 (2005). However, the terms are generally considered synonymous and used interchangeably. Cf. Prosecutor v. Akayesu, No. ICTR–96–4–T, para. 629 (Sept. 2, 1998) (“These phrases are so similar that, for the Chamber’s purposes, they may be treated as synonymous.”); Operational Law Handbook 14, 17, 78, 398 (Derek, I. Grimes ed., 2005)Google Scholar (using terms “active” and “direct” interchangeably); Melzer, Nils Targeted Killing in International Law 334 (2008)Google Scholar (“[T]he consistent use of the phrase ‘participent directement’ in the same provisions of the equally authentic French treaty texts leaves no doubt that the English terms ‘direct’ and ‘active’ must be interpreted synonymously.”). The distinction, even when framed with great care, is dispositive only in a narrow range of cases, none of which has obvious strategic significance in the conflict with Al Qaeda. See, e.g., U.S. Army, Senior Officer Legal Orientation Deskbook, supra, at 43–11 n.42Google Scholar (“For instance, a civilian truck driver delivering ammunition from a stateside depot to an Army post with units preparing to deploy would likely not constitute taking an active part in hostilities. A civilian delivery of the same ammunition from a deployed forward supply point to the First Sergeant of a unit in contact and low on ammunition, however, would likely satisfy the active part test for taking part in hostilities.”).

19 Geneva Convention Relative to the Treatment of Prisoners of War, Art. 4(A)(4), Aug. 12, 1949, 6 UST3316, 3320,75 UNTS 135 [hereinafter Third Geneva Convention]; see also, e.g., Joint Chiefs of Staff, U.S. Dep’ts of the Army, the Navy, the Air Force, and the Marine Corps, Joint Pub. 4–0, Doctrine For Logistic Support of Joint Operations V–1 to –2 (2000)Google Scholar (defining the combatant category to exclude civilians performing such functions as maintenance of weapon systems, command–and–control infrastructure, and communication systems, as well as construction of roads, airfields, transportation services, and prison facilities); see also Protocol I, supra note 13, Art. 50(1) (defining civilians as “any person who does not belong to one of the categories of persons referred to in Article 4 (A) (1), (2), (3) and (6) of the Third Convention”).

20 See, e.g., Third Geneva Convention, supra note 19, Art. 33.

21 Joint Chiefs of Staff, supra note 19, at V–1.

22 Melzer, supra note 18, at 320.

23 See ICRC, Commentary: IV Geneva Convention Relative To the Protection of Civilian Persons in Time of War, Art. 42, at 254 (Jean, S. Pictet gen. ed., 1958)Google Scholar [hereinafter Geneva IV Commentary]; Prosecutorv. Kordić & Čerkez, No. IT–95–14/2–A, paras. 72–73,620 (Dec. 17, 2004); Prosecutorv. Delalic, No. IT–96–21–A, para. 327 (Feb. 20, 2001); see also HCJ 593/82, Tsemel v. Minister of Defence, [1983] IsrSC 37(3) 365, reprinted in 1984 Pal. Y.B. Int’l L. 164, 171 (applying rule in conflict with terrorist organization); Inter–Am. Comm’n on Human Rights, supra note 12 (applying rule to actions of guerrilla force in civil war); see also supra note 12 (other sources there cited).

24 See, e.g., Geneva IV Commentary, supra note 23, Art. 42, at 257 (“It did not seem possible to define the expression ‘security of the State’ in a more concrete fashion. It is thus left very largely to Governments to decide the measure of activity prejudicial to the internal or external security of the State which justifies internment or assigned residence.”); id. at 258 (“Subversive activity carried on inside the territory of a Party to the conflict or actions which are of direct assistance to an enemy Power both threaten the security of the country; a belligerent may intern people or place them in assigned residence if it has serious and legitimate reason to think that they are members of organizations whose object is to cause disturbances.... To justify recourse to such measures the State must have good reason to think that the person concerned, by his activities, knowledge or qualifications, represents a real threat to its present or future security.”) (footnote omitted); cf. Commentary on the Additional Protocols to the Geneva Conventions, supra note 15, Commentary to Protocol I, Art. 43, at 516, quoted in text at note 16 supra; id., Commentary to Protocol II, Art. 13, at 145 3, quoted in text at note 17 supra; Geneva IV Commentary, supra, Art. 5, at 53–54, 56; Robert, W. Gehring Loss of Civilian Protections Under the Fourth Geneva Convention and Protocol I , 90 Mil. L. Rev. 49, 85 (1980)Google Scholar (“It must be emphasized that the danger which is perceived by the state and which permits such restrictions [internment and assigned residence] is not limited to hostile activity, though that is certainly included.… Even Pictet… suggests that knowledge or qualifications may represent a real threat to the state’s present or future security.”).

25 Fourth Geneva Convention, supra note 7. In international armed conflict, individuals who do not qualify as POWs (and would be detainable as such) are protected by the Fourth Geneva Convention. See, e.g., kJinks, Derek The Declining Significance of POW Status , 45 Harv. Int’l L.J. 367, 380–409 (2004).Google Scholar

26 See supra notes 12, 23.

27 Geneva IV Commentary, supra note 23, Art. 42, at 258.

28 See supra note 19.

29 Bothe, Michael Partsch, Karl Josef & Solf, Waldemar A. New Rules For Victims of Armed Conflicts: Commentary on The Two 1977 Protocols Additional To The Geneva Conventions of 1949, at 672 (1982)Google Scholar (discussing direct participation in context of Protocol II); see also Goldman, Robert Kogod International Humanitarian Law: Americas Watch’s Experience in Monitoring Internal Armed Conflicts , 9 Am. U. J. Int’l L. & Pol’y 49, 71 (1993)Google Scholar (quoting Bothe, Partsch, & Solf, supra, at 672, as quoted in text); Rogers, A. P. V. Law on the Battlefield 29 (2d ed. 2004)Google Scholar (listing a spectrum of actions from direct to indirect participation).

30 See supra note 19 and corresponding text.

31 See infra text at note 36.

32 See supra note 24; cf. Prosecutor v. Kordić & Čerkez, No. IT–95–14/2–T, para. 284 (Feb. 26, 2001), aff’d, No. IT–95–14/2–A, supra note 23.

33 See Geneva IV Commentary, supra note 23, Art. 5, at 56 (the standard “cannot refer to a political attitude towards die State, so long as that attitude is not translated into action”); Prosecutor v. Delalić, No. IT–96 – 2 1 , para. 577 (Nov. 16,1998), aff’d, No. IT–96–21–A, supra note 23; id, para. 567; Kordić & Čerkez, supra note 32, para. 280; cf. Geneva IV Commentary, supra, Art. 42, at 258.

34 Geneva IV Commentary, supra note 23, Art. 42, at 258; CrimA 3261/08, A. v. Israel, para. 21 (2008), available at < (“in order to detain a person it is not sufficient for him to have made a remote, negligible or marginal contribution to the hostilities”); see also Kordić & Čerkez, supra note 33, para. 280; infra notes 35–37 and corresponding text; cf, Delalić, supra note 33, para. 568.

Notably, some authorities suggest that an additional factor circumscribes the class of activities that might qualify as indirect participation: “it is almost certain that the condemned activity will in most cases be the subject of criminal punishment under national law.” Delalić, supra, para. 568; see also Gehring, supra note 24, at 80 n.73; Kordić & Čerkez, supra, para. 280. It is unclear, however, whether this factor imposes any meaningful constraint. Cf. Geneva IV Commentary, supra, Art. 5, at 53 n.2.

35 A. v. Israel, supra note 34.

36 Id., para. 21.

37 Hamdiv. Rumsfeld, 542 U.S. 507,521 (2004) (plurality opinion) (“Certainly, we agree that indefinite detention for the purpose of interrogation is not authorized.”); UN Comm’n on Human Rights, Situation of Detainees at Guantanamo Bay, para. 23, UN Doc. E/CN.4/2006/120 (Feb. 27, 2006) (“The indefinite detention of prisoners of war and civilian internees for purposes of continued interrogation is inconsistent with the provisions of the Geneva Conventions.”); Neil A. Lewis, Red Cross Criticizes Indefinite Detention in Guant&namo Bay, N.Y. Times, Oct. 10, 2003, at A1 (quoting Christophe Girod, senior Red Cross official in Washington).

There is a potential exception with respect to information, but of a wholly different character. An individual may possess information that makes her a danger to the detaining power (e.g., knowledge of vulnerabilities in the detaining power’s defense system). A plausible reading of the ICRC Commentary would permit the use of detention—if it is absolutely necessary—to prevent her from directly assisting the enemy with that type of knowledge. See Geneva IV Commentary, supra note 23, Art. 42, at 258 (“To justify recourse to such measures the State must have good reason to think that the person concerned, by his activities, knowledge or qualifications, represents a real threat to its present or future security”).

For an extended analysis of intelligence gathering as a ground for detention, see Goodman, Ryan Rationales for Detention: Security Threats and Intelligence Value , 85 Int’l L. Stud. (Naval War College, forthcoming 2009).Google Scholar

38 Fourth Geneva Convention, supra note 7, Art. 42.

39 See Geneva IV Commentary, supra note 23, Art. 42, at 257.

40 Richard, R. Baxter The Duty of Obedience to the Belligerent Occupant , 1950 Brit. Y.B. Int’l L. 235, 264 Google Scholar; see also Fourth Geneva Convention, supra note 7, Art. 147 (unlawful confinement constitutes a grave breach).

41 There may be an exception to this rule if (1) an individual’s mere membership in the armed forces renders her a legitimate military target, and (2) mere membership is insufficient and an additional inquiry into the nature and scale of the individual’s contribution is required for detention. The latter proposition was upheld in A v. Israel, supra note 34, para. 21. Of course, one might argue that the holding is accordingly flawed because it violates the maxim that states cannot have the power to kill X person but lack the power to detain Xperson. Note also that the first proposition was recently qualified in an analysis of common Article 3 by the ICTY. Prosecutor v. Halilovic, No. IT–01–48–T (Nov. 16, 2005); id., para. 34 (“While membership of the armed forces can be a strong indication that the victim is direcdy participating in the hostilities, it is not an indicator which in and of itself is sufficient to establish this.”); id. n.78 (providing examples of “a person [who] may be listed as a member of an armed force, without being mobilised…. [and] that in a state of war, the civilian police by law [may] become part of the armed forces”). But see The Handbook of International Humanitarian Law 96–98 (Fleck, Dieter ed., 2d ed. 2008).Google Scholar

42 Two qualifications deserve mention. First, this general statement may turn on the scope of the temporal element of the direct participation standard. Members of the regular armed forces who are off duty or otherwise not participating in hostilities at the time of being attacked are nevertheless legitimate military targets. In contrast, according to some schools of thought, unlawful combatants may be subject to attack only “for so long as” those individuals are directly engaged in fighting or in the imminent stages of preparation. Second, all members of the armed forces, including noncombatant members of the armed forces, may be made the object of attack. In contrast, the members of irregular armed forces who perform noncombatant functions may be indirect participants and thus immune from attack. Melzer, supra note 18, at 320–21.

43 ICRC & TMC Asser Inst., Third Expert Meeting on the Notion of Direct Participation in Hostilities 26–27, Oct. 23–25, 2005, available at <.Google Scholar

44 See supra text at notes 9–11; see also note 9 (discussing applicability of human rights law).

45 See supra notes 25–26 and corresponding text.

46 Geneva IV Commentary, supra note 23, Art. 27, at 207.

47 Fourth Geneva Convention, supra note 7, Art. 42.

48 See supra note 19 and corresponding text.

49 Coard v. United States, Case 10.951, Inter–Am. C.H.R., Report No. 109/99, OEA/Ser.L/V/II.106, doc.6 rev., para. 52 (1999) (“Under exceptional circumstances, international humanitarian law provides for the internment of civilians as a protective measure.”); id., para. 50; id., para. 53 (“The applicable provisions of the Fourth Geneva Convention provide the authorities substantial discretion in making the initial determination, on a case by case basis, that a protected person poses a threat to its security, and the record provides no basis to controvert the security rationale asserted in this case.”); Delalic, supra note 33, para. 576; Tsemel v. Minister of Defence, supra note 23, at 166–67.

50 On Korea, see, for example, Cranston, John Armistice Negotiations, in Korean War: An Encyclopedia 24, 28 (Sandler, Stanley ed., 2004)Google Scholar; on Vietnam, see, for example, Guenter Lewy, America in Vietnam 285–94 (1980)Google Scholar; U.S. Military Assistance Command, Vietnam, Directive No. 381–11, Exploitation of Human Sources and Captured Documents, para. 5(a) (Aug. 5, 1968), reprinted in George, S. prugh Law At War: Vietnam 1964–1973, App. D at 127 (1975)Google Scholar; on Grenada, see, for example, Coard v. United States, supra note 49, at 21, 46, 48; on Panama, see, for example, John Embry, Parkerson Jr. United States Compliance with Humanitarian Law Respecting Civilians During Operation Just Cause , 133 Mil. L. Rev. 31, 68–69 (1991)Google Scholar; on the first Gulf war, see, for example, An Arrangement for the Transfer of Enemy Prisoners of War and Civilian Internees from the Custody of the British Forces to the Custody of the American Forces, Jan. 31, 1991, reprinted in The Gulf War 1990–91 in International and English Law 348, annex 1 (Lowe, Peter ed., 1993)Google Scholar; on Somalia, see, for example, Margaret, B. Baines The “Legal Vacuum” of Detainee Rights 3, 43 (Apr. 1997)Google Scholar (unpublished thesis, Judge Advocate General’s School); on Haiti, see, for example, id.; on Bosnia–Herzegovina, see, for example, Keith, E. Puis The Principles of the Law of Peace Operations: A Practical Framework for Judge Advocates 58–68 (2001)Google Scholar (unpublished thesis, Judge Advocate General’s School), available at <; and on Kosovo, see, for example, id.

51 See, e.g., Dep’t of Defense, Information Paper: Detention of Civilians, available at <; SC Res. 1546, pmbl. & annex at 11, Letter from Colin Powell, U.S. Secretary of State, to Dr. Ayad Allawi, Prime Minister of the Interim Government of Iraq (June 8, 2004) (“Under the agreed arrangement, the MNF stands ready to continue to undertake a broad range of tasks to contribute to the maintenance of security and to ensure force protection. These include…. internment where this is necessary for imperative reasons of security… . ”).

52 See, e.g., U.S. Army, Reg. No. 190–8, Enemy Prisoners of War, Retained Personnel, Civilian Internees and Other Detainees (Oct. 1, 1997).

53 Anieszka, Jachec–Neale Status and Treatment of Prisoners of War and Other Persons Deprived of Their Liberty, in Perspectives on the Icrc Study on Customary International Humanitarian Law 302, 311 (Wilmshurst, Elizabeth & Breau, Susan eds., 2007)Google Scholar (“In recent decades there have been numerous examples of restricting civilians’ personal liberty on the grounds of security such as the ongoing Israeli–Palestinian conflict or the 1991–92 Gulf War during which Iraqi nationals living in the United Kingdom, Italy and France were interned from the outset of the war.”); Jonathan, F. Vance Civilian Internees—World War II, in Encyclopedia of Prisoners of Warand Internment 79, 79 (Jonathan, F. Vance ed., 2d ed. 2006)Google Scholar (“[Thousands of civilians found themselves facing internment during World War II in virtually every belligerent state.”); Jonathan, F. Vance Civilian Internees—World War I, in id. at 77, 77 (“All belligerent nations interned varying numbers of enemy civilians during World War I.”)Google Scholar; Jonathan, F. Vance Gulf War (1990–91), in id. at 168, 169.Google Scholar

54 See, e.g., UN Comm’n on Human Rights, General Comment No. 29, States of Emergency (Article 4), UN Doc. CCPR/C/21/Rev.l/Add.11 (2001); Lawless v. Ireland, 1 Eur. Ct. H.R. (ser. A) (1961).

55 Goodman & Jinks, supra note 7, at 2654–58.

56 See supra notes 17–18 and corresponding text.

57 Third Geneva Convention, supra note 19, Art. 84.

58 See Fourth Geneva Convention, supra note 7, Art. 66.

59 See, e.g., UN Human Rights Comm., Madani v. Algeria, Comm. No. 1172/2003, para. 8.7, UN Doc. CCPR/C/89/D/1172/2003 (June 21, 2007); see infra sources at note 61.

60 Ex parte Milligan, 71 U.S. 2, 121–22, 132 (1866).

61 Hamdi v. Rumsfeld, 542 U.S. 507, 571 (2004) (Scalia, J., dissenting) (disagreeing with this interpretation of Milligan, but acknowledging its acceptance in Quirin, infra note 62); Curtis, A. Bradley The Story of Ex parte Milligan: Military Trials, Enemy Combatants, and Congressional Authorization, in Presidential Power Stories 93 (Christopher, H. Schroeder & Curtis, A. Bradley eds., 2008)Google Scholar (identifying and criticizing the modern understanding of the Milligan holding).

62 See Ex parte Quirin, 317 U.S. 1, 45–46 (1942) (“We construe the Court’s statement as to the inapplicability of the law of war to Milligan’s case as having particular reference to the facts before it. From them the Court concluded that Milligan, not being a part of or associated with the armed forces of the enemy, was a non–belligerent, not subject to the law of war save as—in circumstances found not there to be present and not involved here—martial law might be constitutionally established.… Wehave no occasion now to define with meticulous carethe ultimate boundaries ofthe jurisdiction of military tribunals to try persons according to the law of war. It is enough that petitioners here, upon the conceded facts, were plainly within those boundaries....”); Hamdi, 542 U.S. at 522–24 (plurality opinion); see also Al–Marri v. Pucciarelli, 534 F.3d 213, 230–31 (4th Cir. 2008) (en banc) (Morz, J., concurring).

63 UN Sub–Comm’n on the Promotion and Protection of Human Rights, Issue of the Administration of Justice Through Military Tribunals, UN Doc. E/CN.4/Sub.2/2002/4 (July 9, 2002) (Louis Joinet) (collecting cases and documenting national state practice); UN Comm’n on Human Rights, Issue of the Administration of Justice Through Military Tribunals, para. 21, UN Doc. E/CN.4/2006/58 (Jan. 13, 2006) (Emmanuel Decaux) (stating that the “Human Rights Committee’s practice over the past 20 years… has only increased its vigilance, in order to ensure that the jurisdiction of military tribunals is restricted to offences of a strictly military nature committed by military personnel,” and listing in that regard “[m]any thematic or country rapporteurs” and the jurisprudence of the major regional human rights commissions and courts); UN Comm’n on Human Rights, Question of the Human Rights of All Persons Subjected to Any Form of Detention or Imprisonment, para. 78, UN Doc. E/CN.4/ 1998/39/Add.1 (Feb. 19, 1998) (Param Cumaraswamy) (“In regard to the use of military tribunals to try civilians, international law is developing a consensus as to the need to restrict drastically, or even prohibit, that practice.”); UN Human Rights Comm., General Comment No. 32, Article 14: Right to Equality Before Courts and Tribunals and to a Fair Trial, para. 22, UN Doc. CCPR/C/GC/32 (Aug. 23, 2007) (“Trials of civilians by military or special courts should be exceptional, i.e. limited to cases where the State party can show that resorting to such trials is necessary and justified by objective and serious reasons, and where with regard to the specific class of individuals and offences at issue the regular civilian courts are unable to undertake the trials.”) (footnote omitted) (citing Madani v. Algeria, supra note 59, para. 8.7 to similar effect); Inter–Am. C.H.R., Report on Terrorism and Human Rights, para. 261, OEA/Ser.L/V/II. 116, doc. 5, rev. 1 corr. (Oct. 22, 2002) (“[M]ost fundamental fair trial requirements cannot justifiably be suspended under either international human rights law or international humanitarian law.... including] the…. right to be tried by a competent, independent and impartial tribunal in conformity with applicable international standards. In respect of the prosecution of civilians, this requires trial by regularly constituted courts that are demonstrably independent from the other branches of government… and generally prohibits the use of ad hoc, special, or military tribunals or commissions to try civilians.”); id., Annex I, Resolution on Terrorism and Human Rights (Dec. 12, 2001) (including a more categorical prohibition: “According to the doctrine of the IACHR, military courts may not try civilians, except when no civilian courts exist or where trial by such courts is materially impossible.”); Öcalan v. Turkey, 2005–IV Eur. Ct. H.R. 131, para. 116 (Grand Chamber); id, para. 8 (Wildhaber, Pres. & J., dissenting) (attempting to distinguish cases by reclassifying defendant as noncivilian); Incal v. Turkey, 1998–IV Eur. Ct. H.R. 1547 (Grand Chamber); cf. Gary D. Solis, Declaration, para. 6.f, Boumediene v. Bush, 583 F.Supp.2d 133 (D.D.C. 2008) (Civ. No. 04–1166 (RJL)), available in 2008 WL 5260271 (“Absent direct participation in hostilities a civilian is not a combatant… and he is not subject to prosecution in a military forum.”).

Some of these authorities rely on international human rights law or do not expressly distinguish international human rights and humanitarian law. The inclusion of human rights law may not be controversial in the present context, because the relevant IHL rules for fair trials (e.g., common Article 3) countenance reference to human rights standards. Additionally, state actions adopted during wartime constitute relevant practice for customary international law of both IHL and human rights law.

64 See, e.g., Inter–Am. C.H.R., supra note 63, para. 232 (“Although… Article 75 of Additional Protocol I [and other provisions of IHL] do not specifically address the susceptibility of [unprivileged] combatants to trial by military courts, there appears to be no reason to consider that a different standard would apply as between privileged and unprivileged combatants.”); id., para. 69 (defining “unprivileged combatants” to include civilian direct participants); see also Dinstein, Yoram The System of Status Groups in International Humanitarian Law, in International Humanitarian Law Facing New Challenges 145, 153 (Wolff Heintschel von, Heinegg & Epping, Volker eds., 2007)Google Scholar (“Although a captured unlawful combatant need not be put on trial at all, he is definitely susceptible to being prosecuted and punished by the domestic (civil or military) courts of the detaining State.”).

65 Hamdi v. Rumsfeld, 542 U.S. 507,516 (2004) (emphasis added) (internal quotation marks omitted) (quoting Brief for the Respondents at 3, Hamdi v. Rumsfeld, 542 U.S. 507 (2004) (No. 03–6696), available in 2004 WL 724020 (quoting U.S. Dep’t of Defense, Fact Sheet: Guantanamo Detainees 5 (Feb. 13, 2004), available at <)).

66 See Deputy Secretary of Defense Paul Wolfowitz, Memorandum to the Secretary of the Navy 1 (July 7, 2004) (emphasis added), available at <.Google Scholar

67 In re Guantanamo Detainee Cases, 355 F.Supp.2d 443, 475 (D.D.C. 2005) (criticizing this definition).

68 Military Commissions Act of 2006, 10 U.S.C. §948a(1)(i) (2006). Some commentators assert that the Act’s definition pertains only to the personal jurisdiction of military commissions. See, e.g., Al–Marri 534 F.3d 213, 328 n.9 (4th Cir. 2008) (Wilkinson, J., concurring in part, dissenting in part). However, sections of the Act concerning detention (and habeas rights in particular) expressly reference the statute’s global definition of enemy combatants. See28 U.S.C. §2241 (2006). The Military Commissions Act also refines and integrates the Detainee Treatment Act, and thus provides the most likely definition for those detention purposes. See also infra note 74 (legislative history concerning application of the Military Commissions Act’s definition of enemy combatant to detention).

69 The U.S. law could be compared with analogous legislation in Israel. The title of the Israeli statute similarly relates to “unlawful combatants,” although its provisions encompass individuals who have taken indirect part in hostilities. Incarceration of Unlawful Combatants Law §2, 2002, SH 179, available at < (stating that “‘unlawful combatant’ means a person who has participated either directly or indirectly in hostile acts against the State of Israel or is a member of a force perpetrating hostile acts against the State of Israel”).

70 The phrase “purposefully and materially supported” does not impose a sufficient constraint. These elements are consistent with “direct assistance” in the indirect participation standard. And as the following analysis shows, the intent and effect of the statute do not preclude the detention of indirect participants. See infra text at notes 71–74.

71 Dep’t of Defense, supra note 65, at 2 (including among “representative examples” of detained combatants individuals “involved in terrorist financing,” “with links to a financier of the September 11th plots,” and “who served as an al Qaida translator and managed operating funds”). Also consider the principal charges against individuals held at Guantánamo and later designated for prosecution before military commissions. According to the initial charge sheets, one detainee allegedly served as an “accountant and treasurer” and “provided logistical support such as food, shelter and clothing”; he also “assisted in loading and transporting” weapons and ammunition. Charge Sheet at 3, United States v. Al Qosi (U.S. Mil. Comm’n 2004), available at <. A second detainee “created several instructional and motivational recruiting video tapes.” Charge Sheet at 3, United States v. Al Bahlul (U.S. Mil. Comm’n 2004), available at <. These allegations alone clearly would not support a finding of direct participation under IHL. Instead, these facts fall squarely within expressly identified examples of indirect participation or nonparticipation. See New Rules For Victims of Armed Conflicts, supra note 29, at 672 (noting that “transporting supplies, serving as messengers or disseminating propaganda” does not constitute direct participation).

72 10 U.S.C. §948a (2006).

73 152 Cong. Rec. S10, 251 (daily ed. Sept. 27, 2006) (statement of Sen. Graham); see also id. at S10, 250 (statement of Sen. Warner) (“It is only directed at aliens—aliens, not U.S. citizens—bomb–makers, wherever they are in the world; those who provide the money to carry out the terrorism, wherever they are… . ”).

74 Id. at S10, 356 (daily ed. Sept. 28, 2006) (statement of Sen. Leahy); id. at S10, 244 (daily ed. Sept. 27, 2006) (statement of Sen. Levin) (describing the changes in the bill from one that “defined the term ‘unlawful combatant’ in accordance with the traditional law of war” to one that classifies an individual as an enemy combatant “regardless of whether that person actually meets the test of engaging in hostilities against the United States or purposefully and materially is supporting such hostilities”); id. at S10, 400 (statement of Sen. Kennedy) (“The bill… works profound and disastrous changes in our law. This legislation sets out an overly broad definition of unlawful enemy combatant.”).

75 In re Guantanamo Detainee Cases, 355 F.Supp.2d 443, 475 (D.D.C. 2005) (citations omitted).

76 2 ICRC, supra note 12, at 113.

77 10 U.S.C. §904 (2006).

78 See infra p. 70.

79 Al–Marri v. Pucciarelli, 534 F.3d 213 (4th Cir. 2008) (en banc) (Motz, J., concurring). Judge Motz’s opinion was formally designated the “plurality opinion” because it represented the largest number of judges supporting the judgment to reverse the district court. That is, Judge Motz’s opinion supported the holding that the petitioner had not been afforded sufficient process to challenge his designation as an enemy combatant. However, the court of appeals also held—contra Judge Motz’s opinion—that Congress had empowered the president to detain the petitioner as an enemy combatant. Notably, Judge Motz’s conclusion that traditional law–of–war principles do not authorize the detention of civilians also commanded a plurality of the court. However, that legal question constituted a subissue that was not critical to either holding.

80 Id. at 227.

81 Id. a t 228 n. 11.

82 Corrected Brief of Appellants at 21–22, l–Marri v. Wright, 487 F.3d 160 (4th Cir. 2007) (No. 06–7427), available at < (emphasis added) (citations omitted); see also Brief for Center for National Security Studies et al. Supporting Petitioner and Reversal at 6–7, 12, Al–Marri v. Wright, supra, available in 2006 WL 3670672.

83 Petition for Writ of Certiorari at 27, Al–Marri v. Pucciarelli, 534 F.3d 213 (4th Cir. 2006), petition for cert, filed, 77 U.S.L.W. 3184 (U.S. Sept 19, 2008) (No. 08–368), available at < (emphasis added); see also id. at 29 (“Neither this Court’s decisions nor established law–of–war principles allow the government to expand military jurisdiction to reach a person lawfully residing in the United States who is unaffiliated with the armed wing of an enemy government and who was never present, let alone participated in hostilities, on a battlefield where U.S. or allied forces were engaged in military operations.”).

84 Brief for the Petitioners at 41–42, Boumediene v. Bush, 128 S.Ct. 2229 (2008) (No. 06–1195), available at < (emphasis added); see also id. at 43 n.44 (stating that “it is far from clear that the laws of war authorize indefinite military detention of civilians under any circumstances”) (citing Brief Amicus Curiae of National Institute of Military Justice, infra note 85).

85 Brief Amicus Curiae of National Institute of Military Justice in Support of Petitioners at 21, Boumediene v. Bush; Al–Odah v. United States, 128 S.Ct. 2229 (2008) (Nos. 06–1195, 06–1196), available at <.

86 See, e.g., Ip, John Comparative Perspectives on the Detention of Terrorist Suspects , 16 Transnat’l L. & Contemp. Probs. 773, 814–16 (2007).Google Scholar

87 See Fourth Geneva Convention, supra note 7, Arts. 43, 78, 132; Protocol I, supra note 13, Art. 75(3).

88 For example, the conflict with Al Qaeda and its affiliates may last decades. Even though continual review may occur for individual detainees, the outer limit—permitting their detention until the cessation of hostilities—may result in confinement that lasts longer than most criminal sentences because of the nature of the particular conflict. Notably, some of these concerns may be ameliorated by decisions of the Obama administration to conform to other aspects of the IHL regime such as introducing (externally verifiable) safeguards for conditions of confinement and meaningful review of individual cases. Those considerations, however, are beyond the scope of the present discussion. See supra note 7 and corresponding text (explaining conditions of confinement and procedural safeguards as a separate prerequisite for detention authority).

89 Ex pane Milligan, 71 U.S. 2 (1866).

90 Hamdi, 542 U.S. 507, 522 (2004) (citations omitted); see also Padilla v. Hanft, 423 F.3d 386, 397 (4th Cir. 2005).

91 Hamdi, 542 U.S. at 567–68 (Scalia, J., dissenting).

92 Al–Marri, 534 F.3d 213, 237 n.19 (4th Cir. 2006).

93 Id.

94 Id. at 230–31. A similar analytic move occurs in the appellants’ brief on behalf of al–Marri. Corrected Brief of Appellants, supra note 82, at 31–32 (“Quirin reinforces Milligan’s core holding that military jurisdiction over individuals in the United States requires that they be combatants under longstanding law of war principles. The Quirin saboteurs were admitted combatants; Milligan was not and al–Marri is not.”); see also Brief for the Petitioners (Boumediene), supra note 84, at 37 n.34; Brief for Center for National Security Studies et al. Supporting Petitioner and Reversal, supra note 82, at 9–10, 12.

95 See also Al–Marri, 534 F.3d at 235–36 & 236 n. 18 (arguing that artificially defining a civilian as a combatant for detention purposes is the same as artificially defining a civilian as a combatant for military trial); see also Petition for Writ of Certiorari (Al–Marri), supra note 83, at 29.

96 Al–Marri, 534 F.3d at 237 (quoting Hamdi, 542 U.S. at 522) (emphasis added). Judge Motz also refers to “the Milligan Court’s express rejection of the Government’s argument that Milligan, even if not subject to military trial, could be held by the military as a prisoner of war during the duration of hostilities.” Id. at 236–37 (citing Milligan, 71 U.S. at 131).

97 Hamdi, 542 U.S. at 522.

98 An Act Relating to Habeas Corpus, and Regulating Judicial Proceedings in Certain Cases, §2, 12 Stat. 755 (1863).

99 Id. These conditions on detention and release of individuals who aided and abetted the enemy were unexceptional. A year earlier, an order of the Department of the Pacific directed that military commanders “will promptly arrest and hold in custody all persons against whom the charge of aiding and abetting the rebellion can be sustained, and under no circumstances will such persons be released without subscribing the oath of allegiance to the United States.” Winthrop, William Military Law and Precedents 827 (2d rev. ed. 1920)Google Scholar; cf Anthony, F. Renzo Making a Burlesque of the Constitution: Military Trials of Civilians in the War Against Terrorism , 31 Vt. L. Rev. 447, 476 n.137 (2007)Google Scholar (stating that “General Wright, head of the Department of the Pacific, ordered the arrest and detention—but not the trial—by military authorities of persons ‘aiding and abetting the rebellion’ “ (emphasis added)). The Lieber Code, published in 1863, also provided that “[t]he commander of an occupying army may require of the civil officers of the enemy, and of its citizens, any pledge he may consider necessary for the safety or security of his army, and upon their failure to give it he may arrest, confine, or detain them.” U.S. War Dep’t, Instructions for the Government of the Armies of the United States in the Field by Order of the Secretary of War, General Orders No. 100, Art. 134 (Apr. 24, 1863); see also Klaus, Samuel Introduction to The Milligan Case 3, 10 (Klaus, Samuel ed., 1929).Google Scholar

100 Milligan, 71 U.S. at 131 (“If the military trial of Milligan was contrary to law, then he was entitled, on the facts stated in his petition, to be discharged from custody by the terms of the act of Congress of March 3d, 1863…. [T]he court was required to liberate him on taking certain oaths prescribed by the law, and entering into recognizance for his good behavior.”); see also id. at 135 (Chase, C.J., dissenting).

101 Corrected Brief of Appellants, supra note 94, at 22 (“If al–Marri is a ‘combatant,’ as the President claims, he—and anyone else the President alleges is ‘associated with al Qaeda’—could lawfully be shot in broad daylight on the streets of the United States.”); Brief for the Petitioners (Boumediene), supra note 84, at 42–43; cf Brief Amicus Curiae of National Institute of Military Justice in Support of Petitioners, supra note 85, at 17–18, 21, 25.

102 Al–Marri, 534 F.3d at 315 (Wilkinson, J., concurring in part, dissenting in part) (“The principle of discrimination requires warring nations to limit their military targets to those persons who actually pose a military threat. At the same time, it allows warring nations to detain those who do represent a military threat, ensuring that such persons, but only those persons, are removed from the field of conflict.”); id. at 319 (Wilkinson, J.) (“[O]nly enemy combatants, both lawful and unlawful, (and civilians who take a direct part in hostilities) may be detained by the military in accordance with the laws of war.”).

103 Brief of Petitioner–Appellee at 32, Padilla v. Hanft, 432 F.3d 582 (4th Cir. 2005) (No. 05–6396), available in 2005 WL 1410172 (“Where the military has authority to shoot enemy soldiers, such as on the battlefield in Afghanistan, the military has power to capture and detain those soldiers instead for some period of time. But unless the government genuinely contends it had the right to shoot Padilla where he was seized by the military—in a jail cell in Manhattan—there is no necessarily–included power to detain him militarily instead, let alone a clearly stated power to do so.”); Brief for the Petitioners (Boumediene), supra note 84, at 36 (“The [Authorization for Use of Military Force’s] implied authorization to detain, however, does not extend to persons who could not properly be subjected to military force (including the imposition of detention) under the long–understood laws of war.”); id. at 40, 42–43, 43 n.44. Butcf.id. at 41 n.41. In contrast, for an example of an analysis that is conscious of potential differences between targeting and detention and, therefore, argues primarily on normative grounds for importing some rules from one domain into the other, see Matthew, C. Waxman Detention as Targeting: Standards of Certainty and Detention of Suspected Terrorists , 108 Colum. L. Rev. 1365 (2008).Google Scholar

104 Thomas, M. Franck The Power of Legitimacy Among Nations 52 (1990)Google Scholar; cf. Chayes, Abram & Chayes, Antonia Handler The New Sovereignty: Compliance With International Regulatory Agreements 10, 126–27 (1995).Google Scholar

105 Andrew, T. Guzman A Compliance–Based Theory of International Law , 90 Cal. L. Rev. 1823, 1863 (2002)Google Scholar; Kenneth, W. Abbott & Snidal, Duncan Hard and Soft Law in International Governance , 54 Int’l Org. 421, 427 (2000).Google Scholar

106 See supra note 2.

107 See supra note 19.

108 See infra note 119 and corresponding text (discussing in particular U.S. obligations under the new Protocol on Children in Armed Conflict).

109 For example, if the government is disabled from preventively detaining individuals, the administration and receptive judges might support theories of criminal liability for mere membership in an organization or they might support the expansion of conspiracy charges in general. An amicus brief on behalf of detainees, oddly enough, suggests pursuing the latter path. Brief for Center for National Security Studies et al. Supporting Petitioner and Reversal, supra note 82, at 15 (“The government need not wait for an actual attack to occur before intervening to apprehend a suspected terrorist. That is what the law of criminal conspiracy is for.”).

110 These situations assume that the decision makers exercise some control over fair–trial rights but cannot expect to exercise direct control over detention rights. Consider, for example, a judge on a military commission, a federal district court judge presented with a case involving jurisdiction of military courts, or an administration official drafting new procedures for terrorism trials.

111 The U.S. government may independently be interested in watering down the direct participation limit on targeting. As the discussion in the text suggests, those efforts risk dangerous and unjustified expansions of targeting authority.

112 The temporal element of the direct participation standard—civilians lose immunity from attack only “for such time” as they directly participate in hostilities— has arguably been eliminated or softened in targeting contexts. Hence, the spillover consequences are even greater than one might otherwise imagine.

113 UN Human Rights Council, Report of the Special Rapporteur on the Promotion and Protection of Human Rights and Fundamental Freedoms While Countering Terrorism, Martin Scheinin, para. 42, UN Doc. A/HRC/6/17/Add.3 (Nov. 22, 2007) (“emphasiz[ing] that while the targeting of a combatant directly participating in hostilities is permitted under the laws of war, there are no circumstances in which the targeting of any other person can be justified”).

114 U.S. Diplomatic Mission to the UN in Geneva, United States Comments on the Report on the Mission to the United States of America of the Special Rapporteur on the Protection and Promotion of Human Rights and Fundamental Freedoms While Countering Terrorism, Martin Scheinin, at 16, para. 42, available at < (emphasis added).

115 Criminal defendants charged for acts of “terrorism,” for example, could argue that the targets of their violence contributed to the enemy’s war effort.

116 International Convention for the Suppression of the Financing of Terrorism, Dec. 9, 1999, 39 ILM 270 (2000).

117 See, e.g., SC Res. 1566 (Oct. 8, 2004).

118 See, e.g., 22 U.S.C. §2656f(d) (2) (2006) (“the term ‘terrorism’ means premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents”) (emphasis added).

119 The Protocol requires states to ensure that children under the age of eighteen “do not take a direct part in hostilities.” Optional Protocol to the Convention on the Rights of the Child on the Involvement of Children in Armed Conflict, Art. 1, May25, 2000, S. Treatydoc. NO. 106–37, at 32, 33 (2000), 39ILM 1285,1287 (2000).

Upon ratification, the United States adopted the following understanding:

UN, Multilateral Treaties Deposited with the Secretary–General (as of Jan. 2, 2009), available at <; cf. Child Soldiers Accountability Act of 2008, Pub. L. No. 110–340, 122 Stat. 3735, §2442(d) (2008). The U.S. letter of submittal makes plain that the definition in the Protocol and understanding is indistinguishable from the IHL direct participation standard. See S. Treaty Doc. No. 106–37, supra, at 37 (the “term ‘direct’ has been understood in the context of treaties relating to the law of armed conflict (including [ICRC] commentaries on the meaning of the provisions of Protocol I to the Geneva Conventions)”); id. at 38.

120 See also Goodman & Jinks, supra note 7, at 2656.

121 Cf. Coard v. United States, supra note 49, para. 48 (discussing such a solution in an analogous context).

122 UN Human Rights Council, supra note 113, para. 30 (“In the case of persons who might be categorized by the United States as unlawful enemy combatants but who in fact were not involved as combatants in an armed conflict, the possibility arises that civilians [may] be tried by a military commission.”).

123 U.S. Diplomatic Mission to the UN in Geneva, supra note 114, at 12, para. 30 (emphasis added).