1 However, modern IHL also developed in relation to other aspects than the protection of wounded members of armed forces in the field, including neutrality in naval warfare, the codification process of the laws and customs of war and the prohibition and regulation of weapons.

2 However, the first attempts to limit the sovereignty of States vis-à-vis their own citizens at the international level date back to the period following World War I. This was mainly in relation to the protection of certain minorities after the dismantling of the Central Powers; see e.g. Millan R. Casanova, “‘Minority Treaties’ Protection in the Interwar Period: Its Contribution to Maintain the European Order after 1945”, in Ioan Horga and Alina Stoica (eds), Europe a Century after the End of the First World War (1918–2018), Romanian Academy Publishing, Bucharest, 2018, pp. 351–355.

3 International Law Commission (ILC), Report of the International Law Commission on the Work of Its First Session, in Yearbook of the International Law Commission, 1949, p. 281, para. 18.

4 See e.g. Oberleitner, Gerd, Human Rights in Armed Conflict: Law, Practice, Policy, Cambridge University Press, Cambridge, 2015, pp. 53–54CrossRefGoogle Scholar.

5 Fortin, Katharine, “Complementarity between the ICRC and the United Nations and International Humanitarian Law and International Human Rights Law, 1948–1968”, International Review of the Red Cross, Vol. 94, No. 888, 2012, pp. 1440–1450CrossRefGoogle Scholar.

6 See e.g. Milanovic, Marko, “A Norm Conflict Perspective on the Relationship between International Humanitarian Law and Human Rights Law”, Journal of Conflict and Security Law, Vol. 14, No. 3, 2010, p. 460Google Scholar.

7 United Nations, Final Act of the International Conference on Human Rights, Tehran, 22 April to 13 May 1968, 1968, p. 18, available at: https://legal.un.org/avl/pdf/ha/fatchr/Final_Act_of_TehranConf.pdf (all internet references were accessed in February 2022).

8 UNGA Res. 2444 (XXIII), 19 December 1968.

9 In paragraph 2 of Resolution 2444, which endorses Resolution XXIII, the resolution “[i]nvites the Secretary-General, in consultation with the International Committee of the Red Cross and other appropriate international organizations, to study … [t]he need for additional humanitarian international conventions or for other appropriate legal instruments to ensure the better protection of civilians, prisoners and combatants in all armed conflicts and the prohibition and limitation of the use of certain methods and means of warfare”.

10 See e.g. the view upheld by some States in relation to the protection of journalists in armed conflicts: Respect for Human Rights in Armed Conflicts: Protection of Journalists Engaged on Dangerous Missions: Argentina, Austria, Colombia, Finland, France, Iran, Japan, Madagascar and Senegal: Revised Draft Resolution, UN Doc. A/C.3/L.1797/Rev. 3, 30 November 1970.

11 Certain reprisals were already prohibited in the Geneva Conventions: see Geneva Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field of 12 August 1949, 75 UNTS 31 (entered into force 21 October 1950) (GC I), Art. 46; Geneva Convention (II) for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea of 12 August 1949, 75 UNTS 85 (entered into force 21 October 1950) (GC II), Art. 47; 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. 13; Geneva Convention (IV) relative to the Protection of Civilian Persons in Time of War of 12 August 1949, 75 UNTS 287 (entered into force 21 October 1950) (GC IV), Art. 33. That list has been extended under AP I: see 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), Arts 20, 51(6), 52(1), 53(c), 54(4), 55(2), 56(4).

12 The Martens Clause first appeared in the preamble of the 1899 Hague Convention. It was repeated in the Geneva Conventions in the final provisions dealing with the execution of the Conventions: see GC I, Art. 63; GC II, Art. 62; GC III, Art. 142; GC IV, Art. 158. It is only with AP I that the Martens Clause has been given a prominent place and a general scope as it has been put in Article 1, as part of the general provisions of the Protocol.

13 See 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, paras 4515, 3005.

14 See e.g. Gaggioli, Gloria, L'influence mutuelle entre les droits de l'homme et le droit international humanitaire à la lumière du droit à la vie, Pedone, Paris, 2013, p. 106Google Scholar.

15 Note that, already in 1967, the UN General Assembly “considered that essential and inalienable human rights should be respected even during the vicissitudes of war” in relation to humanitarian assistance in the Middle East (UNGA Res. 2252 (ES-V), 4 July 1967), whereas the 1968 Tehran Conference adopted a specific resolution on “Respect for and Implementation of Human Rights in Occupied Territories” (United Nations, above note 7, p. 5), later endorsed by the UN General Assembly in a resolution having the same title (UNGA Res. 2443 (XXIII), 19 December 1968).

16 UNGA Res. 2675 (XXV), 9 December 1970 (emphasis added). See also e.g. UNGA Res. 3318 (XXIX), 14 December 1974.

17 See e.g. below notes 83–89.

18 IHRL might also impact IHL itself through a normative rather than a mere interpretative process, by inspiring secondary norms applicable to IHL or incorporating IHRL content into primary (conventional or customary) IHL norms. However, this process remains quite limited. There are a few cases of IHRL impact on the secondary norms applicable to IHL; these arguably include the non-reciprocal character of IHL treaty obligations and the current trend towards recognizing IHL as bestowing rights to individuals rather than merely imposing obligations upon States (see. e.g. Meron, Theodor, “The Humanization of Humanitarian Law”, American Journal of International Law, Vol. 94, No. 2, 2000, pp. 247–252CrossRefGoogle Scholar). With respect to primary IHL norms, no IHL treaty incorporating IHRL norms, as the two Additional Protocols did in 1977, has since been adopted. On the other hand, while the ICRC Customary Law Study suggests that IHRL has been incorporated into customary IHL norms (Jean-Marie Henckaerts and Louise Doswald-Beck (eds), Customary International Humanitarian Law, Vol. 1: Rules, Cambridge University Press, Cambridge, 2005 (ICRC Customary Law Study), available at: https://ihl-databases.icrc.org/customary-ihl/eng/docs/v1), it is argued that the concerned Rules, in particular Rule 99, dealing with detention, and Rule 100, concerning the fair trial guarantees, amount to a “disguised” application and interpretation process respectively. Regarding Rule 99, this is already noticeable in the title of that Rule, which prohibits “arbitrary detention”, those terms being specific to the IHRL narrative. It is even more apparent with respect to the procedural guarantees claimed by the ICRC to be applicable in non-international armed conflict (NIAC), especially the right of habeas corpus (ibid., pp. 351–352), which is entirely based upon human rights practice and case law. Such “disguised” application is contentious since, unlike in the traditional application process (discussed below), these IHRL guarantees, including the right of habeas corpus, are incorporated into IHL and bind armed groups. Regarding Rule 100, the ICRC interpreted the fair trial guarantees applicable to any armed conflict, including NIACs, notably in light of human rights treaties and case law, as incorporating certain IHRL requirements, such as the right to be tried “without undue delay” (ibid., p. 363), although those requirements are provided by IHL treaties only with respect to specific protected persons in international armed conflict (IAC).

19 See e.g. International Criminal Tribunal for the former Yugoslavia (ICTY), The Prosecutor v. Milorad Krnojelac, Case No. IT-97-25-T, Judgment (Trial Chamber), 15 March 2002, para. 181. See also ICTY, The Prosecutor v. Anto Furundžija, Case No. IT-95-17-1-T, Judgment (Trial Chamber), 10 December 1998, paras 143 ff.; ICTY, The Prosecutor v. Zejnil Delalić et al., Case No. IT-96-21-T, Judgment (Trial Chamber), 16 November 1998, paras 452–493, 534–542.

20 See e.g. ICTY, Delalić, above note 19, paras 534–540.

21 See e.g. ICTY, The Prosecutor v. Dragoljub Kunarac et al., Case Nos IT-96-23-T, IT-96-23/1-T, Judgment (Trial Chamber), 22 February 2001, paras 519–520; ICTY, Krnojelac, above note 19, para. 353.

22 For less recent ICRC practice, see e.g. ICRC Customary Law Study, above note 18, p. xxxi.

23 See in particular 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, 2016 (ICRC Commentary on GC I), paras 39–41; ICRC, Commentary on the Second Geneva Convention: Convention (II) for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea, 2nd ed., Geneva, 2017 (ICRC Commentary on GCII), paras 41–42; ICRC, Commentary on the Third Geneva Convention: Convention (III) relative to the Treatment of Prisoners of War, 2nd ed., Geneva, 2020 (ICRC Commentary on GC III), paras 99–105, available at: https://tinyurl.com/5yf9ta5n. The updated ICRC Commentary on GC III is much more developed on this issue than the two other Commentaries.

24 In relation to cruel/inhumane treatment, see e.g. ICRC Commentary on GC III, above note 23, paras 651–659, particularly para. 655 fn. 417, as well as paras 665–669; in relation to torture, see e.g. ibid., paras 662–681, particularly paras 662, 668, 673 fn. 474, 674 (with examples of torture taken from IHRL case law), 681.

25 See e.g. ibid., paras 710–731, particularly paras 715, 718, 723, 724, 728.

26 See ibid., paras 744–751, particularly paras 746, 749.

27 See ICRC Commentary on GC I, above note 23, para. 1968 fn. 20.

28 See ICRC Commentary on GC III, above note 23, para. 2090 fn. 32.

29 See ibid., paras 2536 ff.

30 ICC, The Prosecutor v. Al Hassan Ag Abdoul Aziz Ag Mohamed Ag Mahmoud, Case No. ICC-01/12-01/18-461-Corr-Red, Corrigendum to the Decision on the Confirmation of Charges (Pre-Trial Chamber), 13 November 2019.

31 Ibid., paras 378–380.

32 Ibid., paras 383–384; see also paras 483, 492.

33 However, it is worth observing that no interpretation of IHL in light of IHRL has been made at all by most other bodies, which are nonetheless competent to rule on IHL violations together with violations of other branches of international law or domestic law. For instance, the International Court of Justice (ICJ) has never undertaken such an interpretation, although it has pronounced on IHL violations in several cases and those violations concerned fundamental guarantees, such as the prohibition against torture, or other rules, like those dealing with the requisition or destruction of properties, whose content could have potentially been clarified in light of IHRL, notably in order to harmonize the norms belonging to the two different regimes: see ICJ, Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v. Uganda), Judgment, ICJ Reports 2005, paras 206–207; ICJ, Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion, ICJ Reports 2004, para. 132. This is also the case with regard to the Eritrea–Ethiopia Claims Commission. Although competent to address violations of both IHL and IHRL, the Commission decided not to consider IHRL given that no party to the case relied on it (regarding the International Covenant on Civil and Political Rights, 16 December 1966 (ICCPR), see Eritrea–Ethiopia Claims Commission, Partial Award: Central Front, Eritrea's Claims 2, 4, 6, 7, 8 and 22, 28 April 2004, para. 25). This is quite unfortunate since the issues put before the Commission concerned matters with respect to which IHRL could have played a clarifying role, such as the conditions of detention of PoWs and civilians, as well as the administration of occupied territories. Finally, numerous fact-finding, inquiry and independent commissions and panels of experts have been given the mandate by UN institutions – either the UN Security Council, the UN Secretary-General, the Commission on Human Rights or the Human Rights Council – to investigate violations of both IHRL and IHL. However, most of them did not proceed to any interpretation of the applicable IHL rules in light of IHRL (see, nonetheless, below note 36), even when they specifically addressed the issue of the relationships between IHL and IHRL.

34 US Supreme Court, Hamdan v. Rumsfeld, Secretary of Defense, et al., 558 US 557, No. 05.184, 29 June 2006, pp. 70-71, available at: www.supremecourt.gov/opinions/05pdf/05-184.pdf.

35 See below note 36; see also The Public Commission to Examine the Maritime Incident of 31 May 2010: The Turkel Commission: Report, Part 1, January 2011 (Report of the Turkel Commission), para. 234, available at: www.gov.il/BlobFolder/generalpage/downloads_eng1/en/ENG_turkel_eng_a.pdf. It has also been argued that the Israel Supreme Court interpreted (customary) IHL in light of IHRL with respect to the use of lethal force against legitimate targets under IHL, in particular civilians directly taking part in hostilities in IACs: see Israel Supreme Court, Public Committee Against Torture v. Government, Case No. HCJ 769/02, 14 December 2006, para. 40. According to the Turkel Commission, the Court “incorporate[d] human rights law into international humanitarian law”: Report of the Turkel Commission, above, p. 232 fn. 809.

36 Regarding the Israel Supreme Court, see Yesh Din – Volunteers for Human Rights and Others v. Israel Defense Forces Chief of General Staff and Others, Case No. HCJ 3003/18, 24 May 2018, paras 39–40; regarding the Commission of Inquiry, see Report of the Detailed Findings of the Independent International Commission of Inquiry on the Protests in the Occupied Palestinian Territory, UN Doc. A/HRC/40/CRP.2, 18 March 2019 (2019 Protests Report), paras 84–93, particularly para. 86, and fn. 100.

37 European Court of Human Rights (ECtHR), Hassan v. The United Kingdom, Appl. No. 29750/09, Judgment (Grand Chamber), 16 September 2014, para. 106. See also Inter-American Commission on Human Rights (IACHR), Report on Terrorism and Human Rights, OEA/Ser.L/V/II.116, Doc. 5 rev. 1 corr., 22 October 2002, para. 143; IACHR, Coard and Others v. United States, Report No. 109/99, Case 10.951, 29 September 1999, para. 58.

38 See the below section on “Elaborated but Confusing Frameworks”.

39 See e.g. ICCPR, Art. 4; European Convention on Human Rights (ECHR), 4 November 1950, Art. 15; American Convention on Human Rights (ACHR), 22 November 1969, Art. 27.

40 See e.g. Geneva Academy of International Humanitarian Law and Human Rights (Geneva Academy), Human Rights Obligations of Armed Non-State Actors: An Exploration of the Practice of the UN Human Rights Council, December 2016, available at: www.geneva-academy.ch/joomlatools-files/docman-files/InBrief7_web.pdf.

41 See e.g. the law regulating the conduct of hostilities, in particular the rules on targeting. On that control requirement regarding the IHL fundamental guarantees, see e.g. Steenberghe, Raphaël van, “Who Are Protected by the Fundamental Guarantees under International Humanitarian Law? Part II: Breaking with the Control Requirement in light of the ICC Case Law”, International Criminal Law Review, Vol. 22, 2022Google Scholar, available at: https://tinyurl.com/yckrrwc3.

42 At the international level, see e.g. Human Rights Committee (HRC), General Comment No. 31, “The Nature of the General Legal Obligation Imposed on States Parties to the Covenant”, UN Doc. CCPR/C/21/Rev.1/Add.13, 26 May 2004, para. 10; at the European level, see e.g. ECtHR, Georgia v. Russia (II), Appl. No. 38263/08, Judgment (Grand Chamber), 21 January 2021, para. 81; at the US level, see e.g. IACHR, Coard, above note 37, para. 37.

43 ICCPR, Art. 14(3).

44 ECHR, Art. 6(1); ACHR, Art. 8(1); African Charter on Human and Peoples’ Rights, 27 June 1981, Art. 7(1)(d).

45 ICC, Al Hassan, above note 30, para. 384.

46 No human rights treaty expressly excludes derogations to those guarantees. In addition, even if the practice of human rights bodies has extended the list of guarantees of due process that may not be subject to any derogation, the aforementioned guarantees have not been included on that list: see e.g. IACHR, Report on Terrorism and Human Rights, above note 37, paras 261–262.

47 See e.g. ICRC Commentary on GC III, above note 23, paras 722–723.

48 See above notes 19–21, 24–26 and 31–32.

49 See e.g. ICTY, The Prosecutor v. Tihomir Blaškić, Case No. IT-95-14-A, Judgment (Appeals Chamber), 29 July 2004, para. 639 fn. 1332; Special Court for Sierra Leone (SCSL), The Prosecutor v. Issa Hassan Sesay et al., Case No. SCSL-04-15-A, Judgment (Appeals Chamber), 26 October 2009, paras 577–579. See also the ICC Elements of Crimes regarding the taking of hostages as a war crime (ICC, Elements of Crimes, The Hague, 2011, pp. 17, 33, available at: https://tinyurl.com/y3d6tebm), which “are ‘largely taken from’ the definition contained in the Hostages Convention” (SCSL, Sesay, above, para. 579).

50 See ICRC Commentary on GC I, above note 23, para. 35; ICRC Commentary on GC II, above note 23, para. 35; ICRC Commentary on GC III, above note 23, para. 94 (emphasis added).

51 ICRC Commentary on GC III, above note 23, para. 95 (emphasis added).

52 See ibid., para. 105.

53 See ibid., para. 1543.

54 See above notes 24–29.

55 See e.g. ICRC Commentary on GCIII, above note 23, para. 750.

56 Ibid., para. 715 (emphasis added).

57 That issue must be distinguished from the potential asymmetry that could result, as we will see in detail below, from the application of IHRL, when IHRL may arguably be said to apply only to one party to the armed conflict, namely the State: see the below section on “Modulating Applicable IHRL Obligations”.

58 ICTY, Kunarac, above note 21, para. 467 (emphasis added).

59 ICRC Commentary on GC I, above note 23, para. 40; ICRC Commentary on GC II, above note 23, para. 41; ICRC Commentary on GC III, above note 23, para. 101 (emphasis added).

60 Regarding less elaborated observations, see also ICTY, Delalić, above note 19, para. 473; ICTY, Furundžija, above note 19, para. 162; ICTY, Krnojelac, above note 19, para. 181.

61 ICTY, Kunarac, above note 21, para. 471.

62 Such emphasis by the Tribunal on the specificity of IHL, justifying the adaptation of the interpretive IHRL norm, has also been expressed in other cases dealing with the definition of torture under IHL: see e.g. ICTY, Krnojelac, above note 19, para. 181.

63 Another adaptation was related to the specific purpose for which the act of violence must be committed in order to amount to an act of torture. In the Furundžija case, the ICTY added the purpose of humiliating the victim to the purposes expressly mentioned in the 1984 Convention Against Torture: ICTY, Furundžija, above note 19, para. 162. While that interpretation has been followed by the Tribunal in the Kvočka case (ICTY, The Prosecutor v. Miroslav Kvočka et al., Case No. IT-98-30/1-T, Judgment (Trial Chamber), 2 November 2001, para. 140), it was rejected later by the ICTY, which argued that this purpose was not yet part of the customary definition of torture under international law (see e.g. ICTY, Krnojelac, above note 19, para. 186).

64 See e.g. ICTY, Delalić, above note 19, para. 473; ICTY, Furundžija, above note 19, para. 162.

65 See ICTY, Kunarac, above note 21, para. 496.

66 See e.g. ICTY, Kvočka, above note 63, para. 138; ICTY, Krnojelac, above note 19, para. 162; ICTY, The Prosecutor v. Anto Furundžija, Case No. IT-95-17/1-A, Judgment (Appeals Chamber), 21 July 2000, para. 148; ICTY, The Prosecutor v. Blagoje Simić et al., Case No. IT-95-9-T, Judgment (Trial Chamber), 17 October 2003, para. 82; ICTY, The Prosecutor v. Radoslav Brđanin, Case No. IT-99-36-T, Judgment (Trial Chamber), 1 September 2004, paras 488–489; ICTY, The Prosecutor v. Fatmir Limaj et al., Case No. IT-03-66-T, Judgment (Trial Chamber), 30 November 2005, para. 240; ICTY, The Prosecutor v. Mile Mrkšić et al., Case No. IT-95-13/1-T, Judgment (Trial Chamber), 27 September 2007, para. 514; ICTY, The Prosecutor v. Ramush Haradinaj et al., Case No. IT-04-84-T, Judgment (Trial Chamber), 3 April 2008, para. 519.

67 See ICTY, Kunarac, above note 21, para. 470; see also ICTY, Delalić, above note 19, para. 473.

68 See ICTY, Kunarac, above note 21, paras 470, 493–495. Regarding such reference to the specificity of international criminal law rather than of IHL to justify adaptations of the notion of torture under IHRL, see ICTY, Furundžija, above note 19, para. 162; ICTY, Furundžija, above note 66, para. 148; ICTY, Brđanin, above note 66, paras 488–489; ICTY, The Prosecutor v. Miroslav Kvočka et al., Case No. IT-98-30/1-A, Judgment (Appeals Chamber), 28 February 2005, para. 283.

69 ICRC Commentary on GC I, above note 23, para. 33; ICRC Commentary on GC II, above note 23, para. 33; ICRC Commentary on GC III, above note 23, para. 92.

70 See above notes 50–51 and corresponding main text.

71 See e.g. Linderfalk, Ulf, “Who are ‘the Parties’? Article 31, Paragraph 3(c) of the 1969 Vienna Convention and the ‘Principle of Systemic Integration’ Revisited”, Netherlands International Law Review, Vol. 55, No. 3, 2008CrossRefGoogle Scholar; see also ILC, Fragmentation of International Law: Difficulties Arising from the Diversification and Expansion of International Law: Report of the Study Group of the International Law Commission, UN Doc. A/CN.4/L.682, 13 April 2006, paras 470–472.

72 See e.g. ICRC Commentary on GC III, above note 23, para. 2541.

73 ICRC Commentary on GC I, above note 23, para. 40; ICRC Commentary on GC II, above note 23, para. 41; ICRC Commentary on GC III, above note 23, para. 101.

74 ICRC Commentary on GC III, above note 23, para. 102.

75 See e.g. the adaptation of the IHRL definition of torture; however, the ICRC merely refers to the ICTY case law on that issue (ICRC Commentary on GC III, above note 23, para. 681). With respect to implicit adaptations, however, regarding the minimum amount of living space that dormitories of PoWs should afford, the ICRC refers to the standard established by the European Committee for the Prevention of Torture and Inhuman or Degrading Treatment or Punishment, but requires Detaining Powers to comply with that standard only “wherever circumstances permit” (ibid., para. 2090 fn. 32).

76 ICC, Al Hassan, above note 30, paras 378 (statutory guarantees), 383 (procedural guarantees).

77 See e.g. the case law described in William Schabas, The International Criminal Court: A Commentary on the Rome Statute, 2nd ed., Oxford University Press, Oxford, 2016, pp. 530–534.

78 See e.g. below notes 110 and 119.

79 See e.g. Marco Sassòli, International Humanitarian Law: Rules, Controversies, and Solutions to Problems Arising in Warfare, Edward Elgar, Cheltenham and Northampton, MA, 2019, p. 216; Laura M. Oleson, “Practical Challenges of Implementing the Complementarity between International Humanitarian and Human Rights Law – Demonstrated by the Procedural Regulation of Internment in Non-International Armed Conflict”, Case Western Reserve Journal of International Law, Vol. 40, No. 3, 2009, p. 451; Heike Krieger, “A Conflict of Norms: The Relationship Between Humanitarian Law and Human Rights Law in the ICRC Customary Law Study”, Journal of Conflict and Security Law, Vol. 11, 2006, p. 275.

80 See e.g. H. Krieger, above note 79, p. 275.

81 See e.g. M. Sassòli, above note 79, p. 216.

82 See the below section on “The Unsatisfactory Traditional Frameworks”.

83 See e.g. HRC, above note 42, para. 11; HRC, “General Comment No. 36 on Article 6 of the International Covenant on Civil and Political Rights, on the Right to Life”, UN Doc. CCPR/C/GC/36, 30 October 2018, para. 64.

84 See e.g. ECtHR, Hassan, above note 37, para. 104.

85 See e.g. IACHR, Report on Terrorism and Human Rights, above note 37, para. 61.

86 See e.g. IACtHR, The Ituango Massacres v. Colombia, Preliminary Objections, Merits, Reparations and Costs, Judgment, Series C, No. 148, 1 July 2006, para. 179.

87 See e.g. ACHPR, Communication 227/99, “Democratic Republic of Congo/Burundi, Rwanda, Uganda”, 29 May 2003, available at: www.achpr.org/sessions/descions?id=138.

88 See e.g. ICJ, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports 1996, para. 106; ICJ, Armed Activities, above note 33, para. 216.

89 See e.g. Report of the International Commission of Inquiry to Investigate All Alleged Violations of International Human Rights Law in the Libyan Arab Jamahiriya, UN Doc. A/HRC/17/44, 12 January 2012 (2012 Libya Report), paras 61, 146; Investigation by the Office of the United Nations High Commissioner for Human Rights on Libya: Detailed Findings, UN Doc. A/HRC/31/CRP.3, 15 February 2016 (2016 Libya Report), para. 20.

90 See the above section on “Unavoidable Interplay: The Issue of the Incorporation of IHRL into IHL”.

91 For practice referring to the nexus requirement, see e.g. Report of the Commission on Human Rights in South Sudan, UN Doc. A/HRC/40/69, 12 March 2019 (2019 South Sudan Report), para. 101; Situation of Human Rights in Yemen, including Violations and Abuses since September 2014: Report of the Group of Eminent International and Regional Experts on Yemen, UN Doc. A/HRC/45/6, 28 September 2020 (2020 Yemen Report 1), para. 67. It is argued that the scope of that test may be determined in light of the nexus requirement for the purpose of establishing criminal responsibility for war crimes; see e.g. M. Sassòli, above note 79, pp. 200–203; on that scope, see e.g. ICTY, Kunarac, above note 21, paras 58–59; ICC, The Prosecutor v. Dominic Ongwen, Case No. ICC-02/04-01/15-422-Red, Decision on the Confirmation of Charges (Pre-Trial Chamber), 23 March 2016, para. 2689.

92 See e.g. Antonio Cassese et al. (eds), Cassese's International Criminal Law, 3rd ed., Oxford University Press, Oxford, 2013, p. 67; M. Sassòli, above note 79, p. 199. See also SCSL, The Prosecutor v. Issa Hassan Sesay et al., Case No. SCSL-04-15-T, Judgment (Trial Chamber), 2 March 2009, paras 1451, 1453. See, in particular, Article 4 of GC III and GC IV, Article 41 of AP I, and the condition of not directly participating in hostilities set out in common Article 3 and Article 4 of Additional Protocol II (APII) regarding the enjoyment of the fundamental guarantees (on the interpretation of these conditions as meaning that those guarantees only protect against inter-party violence, see e.g. Raphaël van Steenberghe, “Who Are Protected by the Fundamental Guarantees under International Humanitarian Law? Part I: Breaking with the Status Requirement in light of the ICC Case Law”, International Criminal Law Review, Vol. 22, No. 3, 2021, pp. 367–369).

93 See nonetheless the ICC view that the protections against rape and sexual slavery apply even to intra-party violence: ICC, The Prosecutor v. Bosco Ntaganda, Case No. ICC-01/04-02/06-1707, Second Decision on the Defence's Challenge to the Jurisdiction of the Court in respect of Counts 6 and 9 (Trial Chamber), 4 January 2017; ICC, The Prosecutor v. Bosco Ntaganda, Case No. ICC-01/04-02/06-1962, Judgment on the Appeal of Mr Ntaganda against the “Second Decision on the Defence's Challenge to the Jurisdiction of the Court in respect of Counts 6 and 9” (Appeals Chamber), 15 June 2017.

94 See e.g. also ECtHR, Georgia v. Russia (II), above note 42, paras 176–199 (pillaging and destruction of properties), 290–291 (internal displacement of persons), 310–311 (pillaging and destruction of schools), 323–325 (failure to investigate).

95 See e.g. 2016 Libya Report, above note 89, paras 149–152; 2020 Yemen Report 1, above note 91, para. 67.

96 See e.g. Report of the Independent International Commission of Inquiry on the Syrian Arab Republic, UN Doc. A/HRC/22/59, 5 February 2013 (2013 Syria Report), Annex XIII, para. 21; Report of the Independent International Commission of Inquiry on the Syrian Arab Republic, UN Doc. A/HRC/27/60, 13 August 2014, para. 132.

97 See e.g. Assessment Mission by the Office of the United Nations High Commissioner for Human Rights to Improve Human Rights, Accountability, Reconciliation and Capacity in South Sudan: Report of the United Nations High Commissioner for Human Rights, UN Doc. A/HRC/31/49, 22 April 2016 (2016 South Sudan Report), para. 46.

98 See e.g. Report of the United Nations Fact-Finding Mission on the Gaza Conflict, UN Doc. A/HRC/12/48, 25 September 2009 (2009 Gaza Report), paras 1096–1106.

99 See e.g. ibid., paras 1300–1322.

100 See e.g. Report of the Human Rights Inquiry Commission Established Pursuant to Commission Resolution S-5/1 of 19 October 2000, UN Doc. E/CN.4/2001/121, 16 March 2001 (2001 Occupied Territories Report), paras 93–94.

101 See e.g. Situation of Human Rights in Yemen, including Violations and Abuses since September 2014: Report of the Group of Eminent International and Regional Experts on Yemen, UN Doc. A/HRC/45/CRP.7, 29 September 2020 (2020 Yemen Report 2), paras 110–147.

102 See e.g. 2001 Occupied Territories Report, above note 100, para. 94; 2012 Libya Report, above note 89, para. 131.

103 See e.g. 2020 Yemen Report 2, above note 101, paras 334–335.

104 See e.g. 2013 Syria Report, above note 96, para. 13; 2016 South Sudan Report, above note 97, para. 46; Report of the International Commission of Inquiry on Darfur to the United Nations Secretary-General, 25 January 2005 (2005 Darfur Report), para. 318, available at: www.un.org/ruleoflaw/files/com_inq_darfur.pdf; 2009 Gaza Report, above note 98, paras 323–324.

105 See e.g. 2012 Libya Report, above note 89, paras 148 (IHL), 150 (IHRL).

106 See e.g. 2020 Yemen Report 2, above note 101, para. 84.

107 See e.g. 2016 South Sudan Report, above note 97, para. 52; 2009 Gaza Report, above note 98, paras 926–941.

108 For a series of conducts regulated by both IHL and IHRL, see e.g. 2019 South Sudan Report, above note 91, paras 96–98; Report of the Commission on Human Rights in South Sudan, UN Doc. A/HRC/43/56, 31 January 2020, paras 26, 66–68.

109 For a similar approach to the notion of normative conflict, see e.g. ILC, above note 71, para. 25. See also M. Sassòli, above note 79, p. 438.

110 One of the first scholars to use this term was Vera Gowlland-Debbas, “The Right to Life and the Relationship between Human Rights and Humanitarian Law”, in Christian Tomuschat, Evelyne Lagrange and Stefan Oeter (eds), The Right to Life, Martinus Nijhoff, Leiden and Boston, MA, 2010, p. 128; see also Hélène Tigroudja, “Les conflits armés”, in Michel Levinet (ed.), Le droit au respect de la vie au sens de la Convention européenne des droits de l'homme, Anthémis, Limal, 2010, p. 215; Jean d'Aspremont and Jérôme de Hemptinne, Droit international humanitaire: Thèmes choisis, Pedone, Paris, 2012, p. 86.

111 ICJ, Nuclear Weapons, above note 88, para. 25.

112 The ICJ again referred to the lex specialis principle with respect to the relationships between IHL and IHRL in the Wall case (above note 33, para. 106), but not in the Armed Activities case (above note 33, para. 216). Regarding the human rights monitoring bodies, see e.g. above notes 83 and 85; regarding the commissions of inquiry and fact-finding missions, see e.g. 2012 Libya Report, above note 89, para. 146; 2005 Darfur Report, above note 104, para. 143; 2001 Occupied Territories Report, above note 100, para. 62; 2019 Protests Report, above note 36, paras 81–83; 2020 Yemen Report 1, above note 91, para. 11; Report of the OHCHR Investigation on Sri Lanka (OISL), UN Doc. A/HRC/30/CRP.2, 16 September 2015 (2015 Sri Lanka Report), para. 178.

113 See ECtHR, Hassan, above note 37, para. 102; ECtHR, Georgia v. Russia (II), above note 42, para. 95.

114 See e.g. IACHR, Franklin Guillermo Aisalla Molina (Ecuador-Colombia), Admissibility Report No. 112/10, Inter-State Petition IP-02, OEA/Ser.L/V/II.140, Doc. 10, 21 October 2010, para. 121.

115 See e.g. ibid., para. 122. Although the Commission relied on the IHL regulation not only to interpret the relevant IHRL norm but also to pronounce on violations of that regulation itself, it ceased such practice after the IACtHR ruled in the Las Palmeras case (Preliminary Objections, Judgment, Series C No. 67, 4 February 2000, para. 33) that the Commission, like itself, was only competent to pronounce on IHRL violations.

116 That formula has been used by the HRC in its General Comment No. 31 (above note 42, para. 11) and repeated by the commissions of inquiry or fact-finding missions established by the Human Rights Council (see e.g. 2016 Libya Report, above note 89, para. 20; Report of The International Fact-Finding Mission to Investigate Violations of International Law, including International Humanitarian and Human Rights Law, Resulting from the Israeli Attacks on the Flotilla of Ships Carrying Humanitarian Assistance, UN Doc. A/HRC/15/21, 27 September 2010, paras 68, 71; 2020 Yemen Report 2, above note 101, paras 178–179).

117 See e.g. M. Sassòli, above note 79, p. 440. However, a less traditional view envisages a qualified habeas corpus to which PoWs should be entitled, in particular “where the detainee (a) challenges his or her status as a prisoner of war; (b) claims to be entitled to repatriation or transfer to a neutral State if seriously injured or ill; or (c) claims not to have been released or repatriated without delay following the cessation of active hostilities” (Report of the Working Group on Arbitrary Detention: United Nations Basic Principles and Guidelines on Remedies and Procedures on the Right of Anyone Deprived of Their Liberty to Bring Proceedings Before a Court, UN Doc. A/HRC/30/37, 6 July 2015, para. 30).

118 ECtHR, Hassan, above note 37, para. 102.

119 M. Milanovic, above note 6, p. 475. It is arguable that the ECtHR would remain competent to adjudicate the case even if it would have to assess the concerned conduct in light of the relevant applicable IHL norm that would have displaced Article 5 of the ECHR; similarly, in relation to Article 2 of the ECHR, see ECtHR, Georgia v. Russia (II), above note 42, Concurring Opinion of Judge Keller, p. 153, para. 25 (and the case law quoted by the judge).

120 On this terminology, see e.g. M. Milanovic, above note 6, p. 465.

121 On this terminology, see ibid.

122 See e.g. ILC, above note 71, para. 56; see also G. Gaggioli, above note 14, p. 59, in which the author distinguishes between the “interpretative” lex specialis and the “derogatory” lex specialis.

123 On those two different paradigms, see e.g. Gloria Gaggioli (ed.), Expert Meeting: The Use of Force in Armed Conflicts: Interplay between the Conduct of Hostilities and Law Enforcement Paradigms, ICRC, Geneva, 2013, pp. 4 –12. See also the below section on “Setting Aside the Applicable IHRL Regime”.

124 See e.g. Vera Gowlland-Debbas and Gloria Gaggioli, “The Relationships between International Human Rights and International Humanitarian Law: An Overview”, in Robert Kolb and Gloria Gaggioli (eds), Research Handbook on Human Rights and International Humanitarian Law, Edward Elgar, Cheltenham and Northampton, MA, 2013, p. 85.

125 Anja Lindroos, “Addressing Norm Conflicts in a Fragmented Legal System: The Doctrine of Lex Specialis”, Nordic Journal of International Law, Vol. 74, No. 27, 2005, p. 42.

126 See e.g. Olson, Laura M. and Sassòli, Marco, “The Relationship between International Humanitarian and Human Rights Law Where It Matters: Admissible Killing and Internment of Fighters in Non-International Armed Conflicts”, International Review of the Red Cross, Vol. 90, No. 871, 2008, pp. 613–614Google Scholar; Ktretzmer, David, Ben-Yehuda, Avias and Furth, Meirav, “Thou Shall Not Kill: The Use of Lethal Force in Non-International Armed Conflicts”, Israel Law Review, Vol. 47, No. 2, 2014, pp. 191 ffGoogle Scholar.

127 M. Milanovic, above note 6, pp. 479, 481.

128 See e.g. ibid., p. 482. The author supports this argument only with respect to conflicts of norms that cannot be solved through a mere interpretation process, but which involve displacing one rule in favour of another. However, as already argued, it seems artificial to distinguish between the interpretation and displacement processes, since both lead to the same result – namely, prioritizing the solution provided by one legal system over the solution provided by the other.

129 L. M. Oleson, above note 79, p. 457.

130 Murray, Daragh, Practitioner's Guide to Human Rights Law in Armed Conflict, Oxford University Press, Oxford, 2016Google Scholar.

131 Ibid., p. 90.

132 Ibid., p. 91.

133 Ibid. These factors include not only the existence of explicit rules on a given conduct but also the fact that those rules are designed for regulating that conduct, the nature of the armed conflict, the existence of active fighting, the status or activity of the individual, and the degree of control exercised by the State.

134 Ibid., p. 90.

135 See e.g. ibid., p. 194.

136 M. Sassòli, above note 79, p. 439.

137 Ibid.

138 Ibid.

139 ILC, above note 71, para. 104.

140 See e.g. Norberto Bobbio, Teoria dell'ordinamento giuridico, G. Giappichelli Ed., Torino, 1960, particularly pp. 69 ff.; Ronald Dworkin, Law's Empire, Fontana Press, London, 1986, particularly pp. 176 ff.; Neil MacCormick, “Coherence in Legal Justification”, in Aleksander Peczenik, Lars Lindahl and Bert Van Roermund (eds), Theory of Legal Science: Proceedings of the Conference on Legal Theory and Philosophy of Science, Lund, Sweden, December 11–14, 1983, D. Reidel, Dordrecht, Boston, MA and Lancaster, 1984, pp. 235 ff.; Vittorio Villa, “Normative Coherence and Epistemological Presuppositions of Justification”, in Patrick Nerhot (ed.), Law, Interpretation and Reality, Kluwer, Dordrecht, Boston MA and London, 1990, pp. 430 ff.; Schiavello, Aldo, “On ‘Coherence’ and ‘Law’: An Analysis of Different Models”, Ratio Juris, Vol. 14, No. 2, 2001, pp. 233 ffCrossRefGoogle Scholar.; Amaya, Amalia, “Ten Theses on Coherence in Law”, in Araszkiewicz, Michael and Savelka, Jaromir (eds), Coherence: Insights, from Philosophy, Jurisprudence and Artificial Intelligence, Springer, Dordrecht, 2013, pp. 257–260Google Scholar.

141 See e.g. Mireille Delmas-Marty, Ordering Pluralism: A Conceptual Framework for Understanding the Transnational Legal World, Hart, Oxford and Portland, OR, 2009.

142 Ibid., pp. 19 ff.

143 N. MacCormick, above note 140, p. 238.

144 See e.g. Robert Alexy, A Theory of Constitutional Rights, Oxford University Press, Oxford, 2002, pp. 57 ff.; Emmanuelle Jouannet, “L'influence des principes généraux face aux phénomènes de fragmentation du droit international contemporain”, in Rosario Huesa Vinaixa and Karel Wellens (eds), L'influence des sources sur l'unité et la fragmentation du droit international, Bruylant, Brussels, 2006, pp. 115 ff.

145 M. Delmas-Marty, above note 141, pp. 39 ff.

146 See e.g. Charles Perelman (ed.), Les antinomies en droit, Bruylant, Brussels, 1965.

147 Charles Huberlant, “Antinomies et le recours aux principes généraux”, in C. Perelman (ed.), above note 146, p. 212 (author's translation).

148 See the introduction to this paper and the above section on “The Interpretation Process Versus the Application Process”.

149 M. Delmas-Marty, above note 141, pp. 39 ff.

150 Ibid.

151 On the approximation of that branch of international law with IHL, see Steenberghe, Raphaël van, “Interactions between International Environmental Law and International Humanitarian Law regarding the Protection of the Environment during Warfare”, Journal of International Criminal Justice, forthcomingGoogle Scholar.

152 See below notes 153–155.

153 See by contrast the project submitted by Jean Pictet in the 1960s to bring IHL and IHRL together within a common legal system that he named “international humanitarian law”: Pictet, Jean, “The Principles of International Humanitarian Law”, International Review of the Red Cross, Vol. 48, No. 573, 1966Google Scholar; Pictet, Jean, “The Principles of International Humanitarian Law – II”, International Review of the Red Cross, Vol. 48, No. 574, 1966Google Scholar; Pictet, Jean, “The Principles of International Humanitarian Law – III”, International Review of the Red Cross, Vol. 48, No. 575, 1966Google Scholar. The project merely involves the juxtaposition of the two bodies of law under a similar heading – except certain principles that Pictet developed and qualified as common to both the Geneva Law and IHRL, like the principles of inviolability, non-discrimination and security.

154 See by contrast the project of “complete and full jus in bello” only briefly advocated by Gerd Oberleitner in his book Human Rights in Armed Conflict (above note 4, p. 124); this project consists of an integrated common regulation on armed conflict built upon the approximations of various regulations applicable in armed conflict, including IHL and IHRL but also other fields of international law, and driven by shared concerns and a quest for coherency.

155 See, by contrast, similar projects that do not however prove specific to armed conflict, such as the project for an “international law common to the protection of individuals”, as advocated by scholars such as Antonio Cançado Trindade (International Law for Humankind: Towards a New Jus Gentium, Martinus Nijhoff, Leiden and Boston, MA, 2010, pp. 511 ff.), or the project that resulted in the 1990 Declaration of Turku (Declaration of Minimum Humanitarian Standards, UN Doc. E/CN.4/Sub.2/1991/55, 2 December 1990), which provides for a series of “minimum humanitarian standards” applicable in any situation.

156 See e.g. M. Milanovic, above note 6, p. 460.

157 H. Victor Condé, A Handbook of International Human Rights Terminology, 2nd ed., University of Nebraska Press, Lincoln, NE, 2004, p. 207, quoted in L. M. Oleson, above note 79, p. 456.

158 Nils Melzer, “Targeted Killing or Less Harmful Means? Israel's High Court Judgment on Targeted Killing and the Restrictive Function of Military Necessity”, Yearbook of International Humanitarian Law, Vol. 9, 2006, p. 104. See also ILC, Report of the International Law Commission on the Work of Its Thirty-Second Session (5 May -25 July 1980), in Yearbook of the International Law Commission, Vol. 2, Part 2, 1980, p. 45, para. 27.

159 See e.g. Koutroulis, Vaios, “And Yet It Exists: In Defence of the ‘Equality of Belligerents’ Principle”, Leiden Journal of International Law, Vol. 26, No. 2, 2013, p. 449CrossRefGoogle Scholar; Keiichiro Okimoto, “The Relationship between Jus ad Bellum and Jus in Bello”, in Marc Weller (ed.), The Oxford Handbook of the Use of Force in International Law, Oxford University Press, Oxford, 2015, p. 1214.

160 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, 2007, p. 659CrossRefGoogle Scholar.

161 See e.g. ICRC Commentary on GC III, above note 23, para. 538; Shany, Yuval, “A Rebuttal to Marco Sassòli”, International Review of the Red Cross, Vol. 93, No. 882, 2011, p. 432Google Scholar; Bugnion, François, “Jus ad Bellum, Jus in Bello and Non-International Armed Conflicts”, Yearbook of International Humanitarian Law, Vol. 6, 2003, p. 186CrossRefGoogle Scholar; M. Sassòli, above note 79, p. 12; J. Somer, above note 160, pp. 659-664.

162 F. Bugnion, above note 161, p. 174.

163 See above note 161.

164 See e.g. V. Koutroulis, above note 159, pp. 449–450 fn. 4.

165 See e.g. Liesbeth Zegveld, Accountability of Armed Opposition Groups in International Law, Cambridge University Press, Cambridge, 2002, pp. 34–35.

166 See e.g. Moussa, Jasmine, “Can Jus ad Bellum Override Jus in Bello? Reaffirming the Separation of the Two Bodies of Law”, International Review of the Red Cross, Vol. 90, No. 872, 2008, p. 99CrossRefGoogle Scholar0.

167 See e.g. Heffes, Ezequiel, “Generating Respect for International Humanitarian Law: The Establishment of Courts by Organized Non-State Armed Groups in Light of the Principle of Equality of Belligerents”, Yearbook of International Humanitarian Law, Vol. 18, 2015, p. 187Google Scholar.

168 See e.g. Jean-Marie Henckaerts and Cornelius Wiesener, “Human Rights Obligations of Non-State Armed Groups: An Assessment Based on Recent Practice”, in Ezequiel Heffes, Marcos D. Kotlik and Manuel J. Ventura (eds), International Humanitarian Law and Non-State Actors: Debates, Law and Practice, Springer, The Hague, 2020, pp. 197–199; SCSL, The Prosecutor v. Sam Hinga Norman, Case No. SCSL-2004-14-AR72(E), Decision on Preliminary Motion Based on Lack of Jurisdiction (Appeals Chamber), 31 May 2004, para. 22.

169 See e.g. J.-M. Henckaerts and C. Wiesener, above note 168, p. 202; Sandesh Sivakumaran, The Law of Non-International Armed Conflict, Oxford University Press, Oxford, 2012, p. 95.

170 See e.g. J. Somer, above note 160, pp. 663–664. Although in unclear terms, the author seems to distinguish the interpretation process, to which the principle of equality is applicable, from the application process, to which the principle is not applicable (ibid., fn. 46).

171 See above notes 19–21, 24–26 and 31–32. Note, however, the ambiguous ICRC assertion in its updated Commentary on GC III: see above note 56 and corresponding main text.

172 See above note 64 and corresponding main text.

173 See ICTY, Kunarac, above note 21, para. 496.

174 See above note 66.

175 See e.g. ICC, above note 49, p. 32.

176 See e.g. ICRC Commentary on GC III, above note 23, para. 681.

177 For a plausible interpretation in that sense, see e.g. ICRC Customary Law Study, above note 18, p. 365, combined with p. xxxi. See also US Supreme Court, Hamdan, above note 34, Dissenting Opinion of Judge Alito, p. 3.

178 The enemy State might have closed those courts before leaving the territory controlled by the armed group: see e.g. cases in Syria (International Legal Assistance Consortium, ILAC Rule of law Assessment Report: Syria 2017, 2017, p. 78, available at: www.ilacnet.org/wp-content/uploads/2017/04/Syria2017.pdf) and the Ivory Coast (Daniel Balint-Kurti, Côte d'Ivoire's Forces Nouvelles, Africa Programme Armed Non-State Actors Series, Chatham House, 2007, p. 27).

179 See e.g. Louise Doswald-Beck, “Judicial Guarantees under Common Article 3”, in Andrew Clapham, Paola Gaeta and Marco Sassòli (eds), The 1949 Geneva Conventions: A Commentary, Oxford University Press, Oxford, 2015, p. 491. This is nonetheless possible, as it occurred in Sri Lanka: see Katrine Fortin, The Accountability of Armed Groups under Human Rights Law, Oxford University Press, Oxford, 2017, p. 164.

180 See e.g. Mark Klamberg, “The Legality of Rebel Courts during Non-International Armed Conflict”, Journal of International Criminal Justice, Vol. 16, No. 3, 2018, p. 9. See also Stockholm District Court, Case No. B 3787-16, Judgment, 16 February 2017, available at: https://casebook.icrc.org/case-study/swedensyria-can-armed-groups-issue-judgments, para. 26; Jonathan Somer, “Opening the Floodgates, Controlling the Flows: Swedish Court Rules on the Legal Capacity of Armed groups to Establish Courts”, EJIL: Talk!, 10 March 2017, available at: www.ejiltalk.org/opening-the-floodgates-controlling-the-flow-swedish-court-rules-on-the-legal-capacity-of-armed-groups-to-establish-courts/.

181 Although the requirement that the courts must be “regularly constituted” still appears in the ICC Elements of Crimes, that requirement means, according to those Elements, that the court must “afford the essential guarantees of independence and impartiality”: ICC, above note 49, p. 34.

182 ICC, Al Hassan, above note 30, paras 375–377.

183 AP II, Art. 6(2).

184 See e.g. ICRC Commentary on GC III, above note 23, para. 728; S. Sivakumaran, above note 169, p. 306. See also the declaration of Nigeria during the preparatory works of AP I: Official Records of the Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts, Geneva (1974–1977), Vol. 8, Berne, 1978, p. 360, para. 20.

185 During the preparatory works of AP II, it was discussed whether Article 6(2)(c) had to include the law of armed groups (see e.g. the declaration of Argentina, in Official Records of the Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts, Geneva (1974–1977), Vol. 9, Berne, 1978, p. 314, para. 54). Although the English version of Article 6(2)(c) refers to the term “law”, which might be interpreted as including the rebels’ law, the French version appears more restrictive as it refers to “national or international law”. However, as argued in the 1987 Commentary on the Additional Protocols (above note 13, para. 4605), the law of armed groups could be considered as a type of national law.

186 Regarding armed groups in Ukraine, see UN Office of the High Commissioner for Human Rights, Report on the Human Rights Situation in Ukraine: 16 February to 15 May 2017, 13 June 2017, para. 94, available at: www.ohchr.org/Documents/Countries/UA/UAReport18th_EN.pdf. Regarding armed groups in Sri Lanka, see Zachariah Cherian Mampilly, Rebel Rulers: Insurgent Governance and Civilian Life during War, Cornell University Press, Ithaca, NY, 2011, p. 116. Regarding armed groups in the Democratic Republic of the Congo, see Human Rights Watch, Seeking Justice: The Prosecution of Sexual Violence in the Congo War, p. 28, March 2005, available at: www.hrw.org/sites/default/files/reports/drc0305.pdf.

187 In that sense, see e.g. UK Ministry of Defence (MoD), The Joint Service Manual of the Law of Armed Conflict, Joint Service Publication 383, 2004, p. 404, para. 15.42 fn. 94; Michael Bothe, Karl Josef Partsch and Waldemar A. Solf, New Rules for Victims of Armed Conflicts: Commentary on the Two 1977 Protocols Additional to the Geneva Conventions of 1949, 2nd ed., Martinus Nijhoff, Leiden, 2013, pp. 745–746; S. Sivakumaran, above note 169, p. 561.

188 See above note 32 and corresponding main text.

189 ICC, Al Hassan, above note 30, para. 379.

190 Ibid. (footnotes omitted).

191 See e.g. Paul Reuter, Droit international public, Presse Universitaire de France, Paris, 1958, pp. 56–59; Paul Reuter, “Principes de droit international public”, Recueil des Cours/Collected Courses, Vol. 103, No. 9, 1962, pp. 598–599; Riccardo Pisillo Mazzeschi, “Due diligence” e responsibilità internazionale degli stati, Giuffrè, Milan, 1992; Riccardo Pisillo Mazzeschi, “The Due Diligence Rule and the Nature of the International Responsibility of States”, German Yearbook of International Law, Vol. 35, 1992; Alexia De Vaucleroy, “Les obligations de comportement en droit international public: Due diligence et responsabilité internationale”, PhD thesis, University of Louvain, 2021.

192 On the origin of obligations of conduct in civil law countries, see e.g. James Crawford, State Responsibility: The General Part, Cambridge University Press, Cambridge, 2013, pp. 221 ff.

193 See e.g. Timo Koivurova, “Due Diligence”, in Max Planck Encyclopedia of Public International Law, 2010, available at: https://tinyurl.com/2p8kmf62.

194 See e.g. R. Pisillo Mazzeschi, “The Due Diligence Rule”, above note 191, pp. 44–45.

195 Regarding the obligations of conduct under IHL, see e.g. Gabriella Venturini, “Les obligations de diligence dans le droit international humanitaire”, in Société Française pour le Droit International and Sarah Cassella (eds), Le standard de due diligence et la responsabilité internationale, Pedone, Paris, 2018; Berkes, Antal, “The Standard of Due Diligence as a Result of Interchange between the Law of Armed Conflict and General International Law”, Journal of Conflict and Security Law, Vol. 23, No. 3, 2018CrossRefGoogle Scholar; Longobardo, Marco, “The Relevance of the Concept of Due Diligence for International Humanitarian Law”, Wisconsin International Law Journal, Vol. 37, No. 1, 2019Google Scholar.

196 See e.g. AP I, Arts 57(2)(a)(i–ii), 57(4), 58.

197 ICRC Customary Law Study, above note 18, p. 54; Protocol on Prohibitions or Restrictions on the Use of Mines, Booby-Traps and Other Devices, as amended 3 May 1996, Art. 3(10); Protocol on Prohibitions or Restrictions on the Use of Incendiary Weapons, 10 October 1980, Art. 1(5). See also the reservations made by certain States to AP I, including the UK, available at: https://tinyurl.com/5b68srmr; France, available at: https://tinyurl.com/y75tj5mu; and Spain, available at: https://tinyurl.com/2e5we5ys.

198 See also the factors listed in the following documents: Protocol on Prohibitions or Restrictions on the Use of Mines, Booby-Traps and Other Devices, above note 197, Art. 3(10); MoD, above note 187, para. 5.32.5; US Department of Defense, Law of War Manual, 2015, para. 5.3.3.2.

199 See e.g. Wolff Heintschel von Heineg, “Precautions in Attack”, in Frauke Lachenmann and Rüdiger Wolfrum (eds), The Law of Armed Conflict and the Use of Force: The Max Planck Encyclopedia of Public International Law, Oxford University Press, Oxford, 2017, p. 1010; Quéguiner, Jean-François, “Precautions under the Law Governing the Conduct of Hostilities”, International Review of the Red Cross, Vol. 88, No. 864, 2006, p. 802CrossRefGoogle Scholar. But see, contra, Canestaro, Nathan A., “Legal and Policy Constraints on the Conduct of Aerial Precision Warfare”, Vanderbilt Journal of Transnational Law, Vol. 37, No. 2, 2004, p. 465Google Scholar.

200 AP II, Art. 5(1).

201 See above notes 188–190 and corresponding main text.

202 See e.g. ICRC Commentary on GC III, above note 23, paras 710–731, particularly paras 715, 718, 723, 724, 728.

203 See e.g. Daragh Murray, Human Rights Obligations of Non-State Armed Groups, Hart, Oxford and Portland, OR, 2016, p. 218.

204 Ibid., p. 217.

205 ICC, Al Hassan, above note 30, para. 379.

206 D. Murray, above note 203, p. 212; see also Marco Sassòli, “Difficulties and Opportunities to Increase Respect for IHL: Specificities of the Additional Protocols”, in 40th Round Table on Current Issues of International Humanitarian Law: The Additional Protocols 40 Years Later: New Conflicts, New Actors, New Perspectives, International Institute of Humanitarian Law, Sanremo, 7–9 September 2017, p. 4.

207 Consequently, civilians could be judged by military courts, although this is only exceptionally allowed under IHRL.

208 For a discussion of that concept, specific to international environmental law, in relation to IHL, see e.g. Gabriella Blum, “On a Differential Law of War”, Harvard International Law Journal, Vol. 1, No. 52, 2011.

209 Regarding the flexibility of due diligence obligations, which “manage to maintain the legal equality of belligerents along with taking into account the factual asymmetries”, see also M. Longobardo, above note 195, p. 85.

210 In that sense, see e.g. Vincent Chétail, “Transfer and Deportation of Civilians”, in A. Clapham, P. Gaeta and M. Sassòli (eds), above note 179, p. 1195.

211 ECHR, Art. 4(3)(a).

212 Forced Labour Convention, 1930, Art. 2(2)(d).

213 See also e.g. Article 2 of Protocol No. 4 to the ECHR securing certain rights and freedoms other than those already included in the Convention and in the first Protocol thereto, as amended by Protocol No 11, 16 September 1963.

214 Regarding such mechanisms of limitation, allowing for exceptions provided by corresponding IHL obligations, see also the limitation provided by Article 8 of the ECHR to the right to respect for private and family life, including the right to correspondence, which enables compatibility with the right of the Detaining Power to limit the number of cards or letters sent and received by detainees under Article 5(2)(b) of AP II; and the limitation on the right to freedom of thought, conscience and religion contained in Article 18 of the ICCPR or Article 9 of the ECHR, which allows compatibility with the right of the Detaining Power to decide whether it is “appropriate” to provide detainees with spiritual assistance under Article 5(1)(d) of AP II.

215 CESCR, General Comment No. 3, “The Nature of States Parties’ Obligations (Art. 2, Para. 1, of the Covenant)”, UN Doc. E/1991/23, 14 December 1990, para. 10.

216 See e.g. ICCPR, Art. 17.

217 See above note 123 regarding the IHRL paradigm with respect to the use of lethal force. See also M. Sassòli, above note 79, pp. 601–603.

218 See above note 123 regarding the IHL paradigm with respect to the use of lethal force. See also M. Sassòli, above note 79, pp. 604–607.

219 See above note 111 and corresponding main text.

220 See e.g. ICCPR, Art. 9; ACHR, Art. 7.

221 This might explain why States are inclined to derogate to IHRL in order to proceed to detention for mere security reasons in NIACs: see e.g. Expert Meeting on Procedural Safeguards for Security Detention in Non-International Armed Conflict, Chatham House and ICRC, London, 22–23 September 2008, p. 7.

222 Regarding the two paradigms, see e.g. M. Sassòli, above note 79, pp. 613–614, 617–619.

223 AP II, Art. 6(5).

224 This is the classical view: see e.g. Lawrence Hill-Cawthorne, Detention in Non-International Armed Conflict, Oxford University Press, Oxford, 2016, pp. 74, 75; Els Debuf, Captured in War: Lawful Internment in Armed Conflict, Pedone and Hart, Paris and Oxford, 2012, pp. 486–488; Rona, Gabor, “An Appraisal of US Practice Relating to ‘Enemy Combatants’”, Yearbook of International Humanitarian Law, Vol. 10, 2007, p. 240CrossRefGoogle Scholar. This view is however contested nowadays: see e.g. Jelena Pejic, “Conflict Classification and the Law Applicable to Detention and the Use of Force”, in Elizabeth Wilmshurst (ed.), International Law and the Classification of Conflicts, Oxford University Press, Oxford, 2012, p. 94; Aughey, Sean and Sari, Aurel, “Targeting and Detention in Non-International Armed Conflict: Serdar Mohammed and the Limits of Human Rights Convergence”, International Law Studies, Vol. 91, 2015, p. 108Google Scholar.

225 For a similar line of questioning, see e.g. J.-M. Henckaerts and C. Wiesener, above note 168, p. 202.

226 See above note 169; see also e.g. M. Sassòli, above note 79, p. 588; K. Fortin, above note 179, p. 337; Yoram Dinstein, Non-International Armed Conflicts in International Law, Cambridge University Press, Cambridge, 2014, pp. 169, 225.

227 See e.g. the practice quoted in S. Sivakumaran, above note 169, p. 88.

228 See e.g. the practice quoted in Christian Tomsuchat, “The Applicability of Human Rights to Insurgent Movements”, in Hans Fischer et al. (eds), Krisensicherung un Humanitärer Schutz – Crisis Management and Humanitarian Protection: Festschrift für Dieter Fleck, Berliner Wissenschaftsverlag, Berlin, 2004, p. 576.

229 Practice quoted in and translated by J.-M. Henckaerts and C. Wiesener, above note 168, p. 203.

230 See above note 126 and corresponding main text.

231 ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts: Report Prepared by the International Committee of the Red Cross for the 32nd International Conference of the Red Cross and Red Crescent, 8–10 December 2015, 2015, p. 35.

232 See above note 224 and corresponding main text.

233 See above note 40 and corresponding main text.

234 See e.g. Tilman Rodenhäuser, who distinguishes between three distinct thresholds (Organizing Rebellion Non-State Armed Groups under International Humanitarian Law, Human Rights Law, and International Criminal Law, Oxford University Press, Oxford, 2018, pp. 147–149).

235 See e.g. Daragh Murray, who supports a context-dependent approach (above note 203, pp. 177–180).

236 See above notes 234–235.

237 See above notes 191 and 195.

238 See above note 200 and corresponding main text.

239 M. Sassòli, above note 79, p. 609.

240 Ibid.

241 Ibid, p. 621..

242 It is worth observing that similar solutions, involving the application of the same but adapted obligations inspired by IHRL to both States and any armed group party to a NIAC, has been advocated by the ICRC through resorting to IHL itself. Regarding the use of lethal force, the ICRC adopted such an approach in the well-known Section IX of its Interpretive Guidance on the Notion of Direct Participation in Hostilities (Interpretive Guidance). Here the ICRC resorted to the IHL concept of military necessity, arguing that the capture and arrest of a lawfully targetable person must be favoured under IHL when the targeting of that person is not justified by military necessity, such as when the person is located in a region firmly controlled by the targeting party: Nils Melzer (ed.), Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law, ICRC, Geneva, 2009, pp. 77–82. This actually comes close to advocating for the application of the relevant IHRL standard to any party to an armed conflict, including NIACs. In addition, the test based on military necessity is context-dependent and enables that standard to be adapted to the circumstances present at the time and in particular the capacities of the parties, as does the standard of due diligence against which the respect for obligations of conduct is to be assessed. Another similar approach has been followed by the ICRC in its Customary Law Study with respect to the issue of detention in NIACs. Here the ICRC identified the customary IHL procedural safeguards on the basis of human rights practice, including the entitlement to habeas corpus, without however defining the precise contours of those safeguards. As already seen (above note 18), this also comes close to the application of the relevant IHRL standards to parties to NIACs. That being said, both approaches have been strongly criticized in legal scholarship: regarding the ICRC position on the use of lethal force in the Interpretive Guidance, see e.g. Parks, W. Hays, “Part IX of the ICRC ‘Direct Participation in Hostilities’ Study: No Mandate, No Expertise, and Legally Incorrect”, New York University Journal of International Law and Politics, Vol. 42, No. 3, 2010Google Scholar; regarding the ICRC's approach to the issue of detention in its Customary Law Study, see e.g. Marco Sassòli, “Taking Armed Groups Seriously: Ways to Improve Their Compliance with International Humanitarian Law”, Journal of International Humanitarian Legal Studies, Vol. 1, No. 1, 2010, p. 17.

243 In that sense, see e.g. M. Sassòli, above note 79, p. 621.

244 ICRC Commentary on GC III, above note 23, para. 2536.

245 Ibid., para. 2538.

246 ICJ, Armed Activities, above note 33, para. 178.

247 ICRC Commentary on GC III, above note 23, para. 2090 fn.32.

248 See e.g. not only Article 30(1) of GC III but also Articles 16, 17, 18, 20 and 22 of GC IV, referring to the “infirm” or “wounded and sick”.

249 In that sense, see also e.g. ICRC, How Law Protects Persons with Disabilities in Armed Conflict, Geneva, 13 December 2017, p 7; Alice Priddy (ed.), Disability and Armed Conflict, Geneva Academy, Geneva, April 2019, pp. 52–53, 56, 69, 77.

250 See HRC, General Comment No. 35, “Article 9 (Liberty and Security of Person)”, UN Doc. CCPR/C/GC/35, 16 December 2014, para. 19.

251 See those quoted in the ICRC Commentary on GC III, above note 23, paras 2242 fn. 33, 2244 fn. 35.

252 See HRC, Thematic Study on the Rights of Persons with Disabilities under Article 11 of the Convention on the Rights of Persons with Disabilities, on Situations of Risk and Humanitarian Emergencies: Report of the Office of the United Nations High Commissioner for Human Rights, UN Doc. A/HRC/31/30, 30 November 2015, paras 10, 47, 55.

253 In that sense, see also ICRC Commentary on GC III, above note 23, para. 2242 fn. 33.

254 See e.g. HRC, Rights of Persons with Disabilities: Report of the Special Rapporteur on the Rights of Persons with Disabilities, UN Doc. A/HRC/40/54, 11 January 2019, para. 27.

255 See e.g. GC III, Art. 89(4).

256 On that narrow conflict, see e.g. Marco Sassòli, “La Cour européenne des droits de l'homme et les conflits armés”, in Stephan Breitenmoser, Bernhard Ehrenzeller and Marco Sassòli (eds), Droits de l'homme, démocratie et Etat de droit: Liber amicorum Luzius Wildhaber, Dike, Zürich, 2007.

257 See e.g. ECtHR, Cyprus v. Turkey, Appl. No. 25781/94, Judgment (Grand Chamber), 10 May 2011, paras 277–278; ECtHR, Incal v. Turkey, Appl. No. 22678/94, Judgment (Grand Chamber), 9 June 1998, paras 70–72.

258 See e.g. M. Sassòli, above note 79, p. 438.

259 See in particular GC IV, Arts 64–77.

260 See in particular AP I, Art. 75.

261 See e.g. Yukata Arai-Takahashi, “Law-Making and the Judicial Guarantees in Occupied Territories,” in A. Clapham, P. Gaeta and M. Sassòli (eds), above note 179, pp. 1438 ff. See also the HRC admitting that civilians are put on trial before military courts but only if such trials are “very exceptional and take place under conditions which genuinely afford the full guarantees stipulated in article 14 [of the ICCPR]”: HRC, Salim Abbassi and Abbassi Madani v. Algeria, Communication No. 1172/2003, UN Doc. CCPR/C/89/D/1172/2003, 28 March 2007.

262 See e.g. GC III, Part III, Section IV; GC IV, Part III, Section IV, Chap. VI.

263 See e.g. GC III, Arts 100, 101; GC IV, Art. 75.

264 See e.g. GC III, Arts 83, 87, 100.

265 See e.g. V. Chétail, above note 210, pp. 1203–1205.

266 See e.g. the exception to the IHRL prohibition on forced or compulsory labour, above notes 211–212, which might enable that prohibition to be compatible with the IHL right of the Detaining Power to oblige certain categories of detainees to work (see e.g. GC III, Art. 49).

267 See e.g. the restrictions on the IHRL right to manifest one's religion or belief (contained notably in Article 18(3) of the ICCPR or Article 9(2) of the ECHR), which might make that right compatible with the IHL limitation on the religious practice of detainees, which is indeed subject to the requirement that it must comply with the disciplinary routine of the camp (Hague Regulations, 1907, Art. 18; GC III, Art. 34; GC IV, Art. 93). On this compatibility, see specifically the ICRC Commentary on GC III, above note 23, para. 2371 fn. 29. For instances of compatibility between IHRL and the law of belligerent occupation, based on the existence of restrictions on the concerned IHRL rights, see e.g. D. Murray, above note 130, pp. 243–244 (right to freedom of expression), 244–246 (right to freedom of movement, right to freedom of association and right to freedom of assembly), 256–257 (right to property).

268 See e.g. the rights provided in the ICESCR, which must be afforded by each contracting party “to the maximum of its available resources” (Art. 2(1)). This enables those rights to be conciliated with IHL norms that do not impose absolute obligations, such as the obligation of the Occupying Power, “[t]o the fullest extent of the means available to it, [to ensure and maintain], with the cooperation of national and local authorities, the medical and hospital establishments and services, public health and hygiene in the occupied territory” (GC IV, Art. 56); the obligation of the Occupying Power, “[t]o the fullest extent of the means available to it, [to ensure] the food and medical supplies of the population” (GC IV, Art. 55); or the obligation of the captor State to take “all feasible precautions … to ensure [the] safety” of those combatants who “have fallen into the power of an adverse Party under unusual conditions of combat which prevent their evacuation” (AP I, Art. 41(3)).

269 See e.g. the human right to correspondence provided in the ICCPR, which prohibits any arbitrary or unlawful interference with correspondence (Art. 17(1)). This enables that right to be cumulatively applied with, for example, the right afforded by IHL to the Detaining Power to limit the correspondence sent by PoWs (GC III, Art. 71) or civilian internees (GC III, Art. 107) and to subject the correspondence sent to or by PoWs (GC III, Art. 76) or civilian internees (GC IV, Art. 112) to censorship.

270 See the above section on “Setting Aside the Applicable IHRL Regime”.

271 See Article 21 of GC III regarding PoWs, and Articles 42 and 78 of GC IV regarding civilian internees.

272 See the above section on “Setting Aside the Applicable IHRL Regime”.

273 See GC IV, Arts 43, 78.

274 Regarding IHRL, see e.g. ICCPR, Art. 9(4); ECHR, Art. 5(4).

275 See above note 117.

276 See e.g. G. Gaggioli, above note 14, p. 52.

277 See above note 126 and corresponding main text.

278 See the above section on “Modulating Applicable IHRL Obligations”.