1 International Court of Justice, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 8 July 1996, para. 78.

2 Protocol Additional (I) to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts, 1125 UNTS 3, 8 June 1977 (entered into force 7 December 1978) (AP I), Art. 48; Henckaerts, Jean-Marie and Doswald-Beck, Louise (eds), Customary International Humanitarian Law, Vol. 1: Rules, Cambridge University Press, Cambridge, 2005CrossRefGoogle Scholar (ICRC Customary Law Study), Rule 1.

3 See Geneva Convention (III) relative to the Treatment of Prisoners of War of 12 August 1949, 75 UNTS 135 (entered into force 21 October 1950) (GC III), Art. 4A; AP I, Arts 43, 52(2).

4 Under the law of IAC, only combatants and civilians who take a direct part in hostilities are legitimate targets (see GC III, Art. 4; AP I, Art. 51(3)). Under the law of NIAC, members of State armed forces, members of armed groups performing a continuous combat function (CCF) and civilians taking a direct part in hostilities are legitimate targets (see Protocol Additional (II) to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts, 1125 UNTS 609, 8 June 1977 (entered into force 7 December 1978) (AP II), Art. 13(3); ICRC Customary Law Study, above note 2, Rules 1, 4).

5 AP I, Art. 51(3); AP II, Art. 13(3); ICRC Customary Law Study, above note 2, Rule 6.

6 Melzer, Nils, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law, ICRC, Geneva, 2009Google Scholar (ICRC Interpretive Guidance), p. 20. See also GC III, Art. 4; AP I, Arts 43, 50(1).

7 See GC III, Art. 4. The four requirements listed in Article 4A(2) of GC III are: being commanded by a person responsible for his subordinates; having a fixed distinctive sign recognizable at a distance; carrying arms openly; and conducting their operations in accordance with the laws and customs of war. It is implicitly assumed that the requirements set out in this section are met by the members of regular armed forces.

8 ICRC Interpretive Guidance, above note 6, p. 21. Article 43 of AP I specifies that “[t]he armed forces of a Party to a conflict consist of all organized armed forces, groups and units which are under a command responsible to that Party for the conduct of its subordinates”.

9 AP I, Art. 43(2).

10 ICRC Expert Meeting, Fourth Expert Meeting on the Notion of “Direct Participation in Hostilities under IHL”, Background Document, Geneva, 27–28 November 2006, p. 12.

11 ICRC Interpretive Guidance, above note 6, p. 27.

12 AP I, Art. 51(3); AP II, Art. 13(3); ICRC Customary Law Study, above note 2, Rule 6.

13 ICRC Interpretive Guidance, above note 6, p. 9.

14 Ibid., p. 13.

15 Corn, Geoffrey and Jenks, Chris, “Two Sides of the Combatant Coin: Untangling Direct Participation in Hostilities from Belligerent Status in Non-International Armed Conflicts”, University of Pennsylvania Journal of International Law, Vol. 33, No. 2, 2011, p. 338Google Scholar.

16 See ICRC Interpretive Guidance, above note 6, p. 25. Without explicitly stating that the CCF concept also applies in IAC, the ICRC specifies that “[m]embership in irregular armed forces, such as militias, volunteer corps, or resistance movements belonging to a party to the conflict, generally is not regulated by domestic law and can only be reliably determined on the basis of functional criteria, such as those applying to organized armed groups in non-international armed conflict”.

17 Ibid., p. 27.

18 For more information on the notion of organized armed groups, see International Criminal Tribunal for the former Yugoslavia (ICTY), Haradinaj et al., Judgment (Trial Chamber I), 3 April 2008, para. 60; ICTY, Prosecutor v. Ljube Boškovski and Johan Tarčulovski, Judgment (Trial Chamber II), 10 July 2008, paras 195–205.

19 Ibid., p. 27.

20 G. Corn and C. Jenks, above note 15, p. 332.

21 ICRC Interpretive Guidance, above note 6, p. 32.

22 Ibid., pp. 32–33.

23 Ibid., p. 33.

24 Ibid., pp. 71–72. The restriction of loss of protection to the duration of specific hostile acts was designed to respond to spontaneous, sporadic or unorganized hostile acts by civilians. This notion of DPH cannot therefore be applied to organized armed groups.

25 Ibid., p. 34.

26 Ibid., p. 34.

27 Ibid., p. 34. For a civilian to be considered as directly participating in hostilities – and therefore lose his/her protection – three criteria need to be fulfilled: threshold of harm, direct causation and belligerent nexus. For more information, see ibid., p. 46.

28 Ibid., p. 72.

29 Ibid., p. 72.

30 ICRC Expert Meeting, Second Expert Meeting: Direct Participation in Hostilities under IHL, Background Document, Geneva, 25–26 October 2004, p. 11.

31 ICRC Expert Meeting, Third Expert Meeting on the Notion of Direct Participation in Hostilities, Summary Report, Geneva, 23–25 October 2005, p. 64.

32 ICRC Interpretive Guidance, above note 6, p. 72.

33 Ibid., p. 72. Also see ICRC, Commentary on the Second Geneva Convention: Convention (II) for the Amelioration of the Condition of the Wounded, Sick and Shipwrecked Members of Armed Forces at Sea, 2nd ed., 2017 (ICRC Commentary on GC II), Art. 3, para. 543.

34 AP I, Art. 50(1).

35 ICRC Interpretive Guidance, above note 6, p. 16.

36 Ibid., p. 16.

37 Ibid., pp. 5–6: “In examining the notion of direct participation in hostilities the ICRC not only had to face longstanding dilemmas that had surrounded its practical application (e.g., can a person be a protected farmer by day and a targetable fighter at night?), but also had to grapple with more recent trends that further underlined the need for clarity. One such trend has been a marked shift in the conduct of hostilities into civilian population centers, including cases of urban warfare, characterized by an unprecedented intermingling of civilians and armed actors.”

38 Ibid., p. 25, 39.

39 Ibid., p. 37. For more information on PMSCs and their involvement in armed conflicts, see Proceedings of the Bruges Colloquium: Private Military/Security Companies Operating in Situations of Armed Conflict, 7th Bruges Colloquium, 19–20 October 2006; Faite, Alexandre, “Involvement of Private Contractors in Armed Conflict: Implications under International Humanitarian Law”, Defence Studies, Vol. 4, No. 2, 2004CrossRefGoogle Scholar.

40 ICRC Expert Meeting, First Expert Meeting: Direct Participation in Hostilities under IHL, Background Paper, 2 June 2003, p. 18.

41 ICRC Interpretive Guidance, above note 6, p. 37.

42 In addition to belonging to a party to the conflict, they must also meet the four requirements listed in Article 4A(2) of GC III. See Cameron, Lindsey, “Private Military Companies: Their Status under International Humanitarian Law and Its Impact on Their Regulation”, International Review of the Red Cross, Vol. 88, No. 863, 2006, p. 585CrossRefGoogle Scholar. It is noted in this article that, in the majority of cases, such persons do not wear distinctive signs or uniforms. It is therefore very rare for PMSC employees to qualify as combatants. Also see Kalidhass, P. R., “Determining the Status of Private Military Companies under International Law: A Quest to Solve Accountability Issues in Armed Conflicts”, Amsterdam Law Forum, Vol. 6, No. 2, 2014Google Scholar.

43 ICRC Interpretive Guidance, above note 6, p. 38. See also L. Cameron, above note 42, p. 582.

44 ICRC Interpretive Guidance, above note 6, p. 38. See also L. Cameron, above note 42, p. 582.

45 L. Cameron, above note 42, p. 577. Such persons may therefore be prosecuted for the mere fact of their participation in hostilities.

46 For more information on this issue, see Hampson, Françoise, “Mercenaries: Diagnosis before Prescription”, Netherlands Yearbook of International Law, Vol. 3, 1991, pp. 14–16Google Scholar; Aldrich, George, “Guerrilla Combatants and Prisoner-of-War Status”, American University International Law Review, Vol. 31, 1982, p. 881Google Scholar. It should also be noted that Article 47 of AP I provides that mercenaries cannot be considered combatants. It might therefore be relevant to consider the possibility of applying the CCF test in the context of IAC. This question will not, however, be further addressed here.

47 ICRC Interpretive Guidance, above note 6, p. 39 (emphasis added).

48 Watkin, Kenneth, “Opportunity Lost: Organized Armed Groups and the ICRC ‘Direct Participation in Hostilities’ Interpretive Guidance”, New York University Journal of International Law and Politics, Vol. 42, 2010, p. 657Google Scholar.

49 ICRC Interpretive Guidance, above note 6, p. 39.

50 GC III, Art. 4A(2).

51 See ibid., Art. 4(2); ICRC Interpretive Guidance, above note 6, p. 22.

52 ICRC Interpretive Guidance, above note 6, p. 22.

53 Ibid., p. 22.

54 Ibid., p. 22.

55 Ibid., p. 23 (emphasis added). According to the Interpretive Guidance, “[t]he concept of ‘belonging to’ requires at least a de facto relationship between an organized armed group and a party to the conflict. This relationship may be officially declared, but may also be expressed through tacit agreement or conclusive behaviour that makes clear for which party the group is fighting”.

56 Ibid., p. 25.

57 Ibid., p. 25.

58 Ibid., p. 25 (emphasis added).

59 Ibid., p. 33.

60 Ibid., pp. 23–24.

61 Ibid., pp. 23–24.

62 Ibid., pp. 23–24.

63 The test for an armed conflict was set out by the ICTY Appeals Chamber in the Tadić decision as follows: “An armed conflict exists whenever there is a resort to armed force between States or protracted armed violence between governmental authorities and organized armed groups or between such groups within a State.” See ICTY, Prosecutor v. Dusko Tadić aka DULE, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, 2 October 1995, para. 70. The Trial Chamber in Tadić interpreted this test in the case of internal armed conflict as consisting of two criteria, namely (i) the intensity of the conflict and (ii) the organization of the parties to the conflict, as a way to distinguish an armed conflict “from banditry, unorganized and short-lived insurrections, or terrorist activities, which are not subject to international humanitarian law”. See ICTY, Prosecutor v. Dusko Tadić aka DULE, Opinion and Judgment, 7 May 1997, para. 562. Following this, the ICTY developed factors that could be taken into account in order to assess the intensity and organization criteria. See ICTY, Prosecutor v. Ljube Boškovski and Johan Tarčulovski, Judgment (Trial Chamber II), 10 July 2008, paras 195–205.

64 For more information on the two criteria required for violence to qualify as a NIAC, see ICRC Commentary on GC II, above note 33, Art. 3, paras 415–459.

65 ICRC Interpretive Guidance, above note 6, p. 24 (emphasis added).

66 Michael N. Schmitt, “The Status of Opposition Fighters in a Non-International Armed Conflict”, Naval War College International Law Studies, Vol. 88, 2012, p. 134.

67 ICRC Interpretive Guidance, above note 6, p. 24.

68 See Corn, Geoffrey, “Mixing Apples and Hand Grenades: The Logical Limit of Applying Human Rights Norms to Armed Conflict”, International Humanitarian Legal Studies, Vol. 52, No. 94, 2010, p. 83Google Scholar; D'Cunha, Samit, “The Notion of External NIACs: Reconsidering the Intensity Threshold in Light of Contemporary Armed Conflicts”, Yearbook of International Humanitarian Law, Vol. 20, 2017, pp. 93–94Google Scholar.

69 S. D'Cunha, above note 68, pp. 93–94.

70 The problem of determining the intensity threshold in an armed conflict is addressed by Samit D'Cunha using an argument similar to the one presented here in relation to the loss of control by a State over an organized armed group. He uses this argument to show that, in certain cases, when there is a loss of control, the intensity threshold for determining the existence of a NIAC should be reconsidered (or even abolished). See ibid., pp. 102–103. The present article puts forward a similar reasoning, arguing that a State's inability to control an organized armed group and exercise its law enforcement powers to respond to the threat it poses does not mean that the group is immune to action against it; in this case, IHL should apply.

71 ICRC Interpretive Guidance, above note 6, pp. 5–6.

72 Such persons could not be regarded as civilians taking a direct part in hostilities because it would be contrary to the intended purpose of the DPH concept, which was developed by the ICRC to cover spontaneous, sporadic and unorganized hostile acts and could not be applied to organized armed groups. The principle of equality of belligerents will be discussed in greater detail later in this article.

73 For more information on the principle of equality of belligerents, see Somer, Jonathan, “Jungle Justice: Passing Sentence on the Equality of Belligerents in Non-International Armed Conflict”, International Review of the Red Cross, Vol. 89, No. 867, 2007CrossRefGoogle Scholar; Roberts, Adam, “The Equal Application of the Laws of war: A Principle Under Pressure”, International Review of the Red Cross, Vol. 90, No. 872, 2008CrossRefGoogle Scholar.

74 ICRC Expert Meeting, Working Sessions IV and V – “Direct Participation in Hostilities” and Membership in Organized Armed Groups, Background Document, Geneva, 23–25 October 2005, pp. 18–19.

75 Israeli High Court of Justice, The Public Committee against Torture v. The Government of Israel, HCJ 769/02, Judgment, 13 December 2006, para. 39.

76 Ibid., para. 39.

77 See above note 63.

78 Commentary on the Geneva Conventions of 12 August 1949, Vol. 1: Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, ICRC, Geneva, 2016, para. 389.

79 For views supporting that common Article 3 contains some regulation of the conduct of hostilities see: Bond, James E, “Application of the Law of War to Internal Conflict”, Georgia Journal of International and Comparative Law, Vol. 3, No. 2, 1973, p. 348Google Scholar; Boothby, William H., The Law of Targeting, Oxford University Press, 2012, p. 433CrossRefGoogle Scholar and Rogers, A.P.V., Law on the Battlefield, 3rd edition, Manchester University Press, 2012, p. 301Google Scholar.

80 ICRC Interpretive Guidance, above note 6, p. 28. Also see ICRC Commentary on GC II, above note 33, Article 3, paras 525–526.

81 ICRC, Commentary on the First Geneva Convention: Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, 2nd ed., Geneva, 2016Google Scholar (ICRC Commentary on GC I), para. 530.

82 Ibid.

83 Kleffner, Jann K., “The Beneficiaries of the Rights Stemming from Common Article 3”, in Clapham, Andrew, Gaeta, Paola and Sassòli, Marco (eds), The 1949 Geneva Conventions: A Commentary, Oxford University Press, Oxford, 2015, p. 440Google Scholar. See also Sandoz, Yves, Swinarski, Christophe and Zimmermann, Bruno (eds), Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949, ICRC, Geneva, 1987Google Scholar, para. 4462, which, on the subject of Article 1 of AP II, states that the term “armed forces” should be interpreted as covering “all the armed forces, including those not included in the definition of the army in the national legislation of some countries”.

84 ICRC Interpretive Guidance, above note 6, pp. 30–31.

85 This article defines who qualifies as a prisoner of war and therefore, indirectly, as a combatant for the purposes of the conduct of hostilities.

86 The ICRC Customary Law Study, above note 2, states that, for the purposes of the principle of distinction in NIAC, the definition of “armed forces” also applies in NIACs (see commentary to Rule 4).

87 ICRC Expert Meeting, above note 10, p. 13.

88 ICRC Interpretive Guidance, above note 6, p. 31.

89 Ibid., p. 31.

90 That is, referring to Article 4A (1) of GC III or Article 43 of AP I.

91 K. Watkin, above note 48, p. 694. They are only considered military targets when they perform a continuous function involving direct participation in hostilities.

92 Melzer, Nils, “Keeping the Balance between Military Necessity and Humanity: A Response to Four Critiques of the ICRC's Interpretive Guidance on the Notion of Direct Participation in Hostilities”, International Law and Politics, Vol. 42, No. 831, 2010, p. 851Google Scholar.

93 ICRC Interpretive Guidance, above note 6, p. 25.

94 K. Watkin, above note 48, pp. 675, 691. Also see Schmitt, Michael N., “The Interpretive Guidance on the Notion of Direct Participation in Hostilities: A Critical Analysis”, Harvard National Security Journal, Vol. 1, 2010, pp. 23–24Google Scholar.

95 It should be noted – although it is not addressed in detail in this paper – that in accordance with the theory presented in this section, members of police forces operating in a NIAC could be considered to be performing a CCF if their actions have a nexus with the conflict in question. It is proposed that when such individuals, who are not generally included in the armed forces of a State, are required to perform a continuous function that involves direct participation in hostilities, they should not be regarded as civilians taking a direct part in hostilities. This proposal would have the advantage of making the law of NIAC more realistic for organized armed groups, as it would allow them to target such persons on a continuous basis and not only when they are taking a direct part in hostilities.

96 Sivakumaran, Sandesh, The Law of Non-International Armed Conflict, Oxford University Press, Oxford, 2012, p. 243Google Scholar.

97 Ibid., p. 245.

98 J. Somer, above note 73, p. 663.

99 ICRC Commentary on GC I, above note 81, para. 530.