1 Carol Morello, “What Tiny Denmark Is Doing to Fight the Islamic State in Syria”, Washington Post, 9 March 2016, available at: https://tinyurl.com/yb9v2xhl (all internet references were accessed in January 2019).

2 Members of the international coalition against Islamic State (IS) include Belgium, Denmark, Estonia, Finland, France, Germany, Italy, Latvia, Lithuania, the Netherlands, Portugal, Romania, Spain, Sweden and the United Kingdom, all of which have reported citizens and/or residents taking part in the armed conflict in Syria and Iraq. The full list of members of the coalition is available at: theglobalcoalition.org/en/partners/. See also Hegghammer, Thomas, “The Rise of Muslim Foreign Fighters”, International Security, Vol. 35, No. 3, 2010/11CrossRefGoogle Scholar.

3 It was estimated in 2016 that about 4,000 people had left Europe to join the Syrian uprising against the Assad regime since its beginning in 2012, 30% of which returned to their countries of departure by 2016. See Bibi van Ginkel and Eva Entenmann, The Foreign Fighters Phenomenon in the European Union: Profiles, Threats & Policies, ICCT Research Paper, 2016, p. 3, available at: https://tinyurl.com/ybc8akux.

4 A foreign fighter is understood for the purposes of this article as an individual who travels to a State other than his or her own State of residence or nationality for the purpose of joining an organized armed group taking part in an armed conflict. See also the definition in Sandra Krähenmann, “Foreign Fighters under International Law”, Geneva Academy of International Humanitarian Law and Human Rights, Briefing No. 7, October 2014, p. 7.

5 Danish Security and Intelligence Service, Vurdering af terrortruslen mod Danmark, 12 January 2018, available at: www.pet.dk/Nyheder/2018/VTD%202018.aspx.

6 The abbreviation “IS” is used throughout the article when referring to the armed group also known as “the so-called Islamic State”, “ISIS”, “ISIL”, “Daesh”, etc.

7 Danish Security and Intelligence Service, above note 5.

8 See ICRC, “Syria: ICRC and Syrian Arab Red Crescent Maintain Aid Effort amid Increased Fighting”, Operational Update, 17 July 2012. For an overview of the conflict in Syria, see Rule of Law in Armed Conflict Project, “Involvement in Armed Conflicts: Syria”, available at: www.rulac.org/countries/syria.

9 For an overview of the current conflict status, see, for example, Christopher M. Blanchard, Carla E. Humud and Mary Beth D. Nikitin, Armed Conflict in Syria: Overview and U.S. Response, RL33487, Congressional Research Service, 24 June 2014, available at: https://fas.org/sgp/crs/mideast/RL33487.pdf.

10 White House Office of the Press Secretary, “President Obama: ‘We Will Degrade and Ultimately Destroy ISIL’”, 10 September 2014, available at: https://obamawhitehouse.archives.gov/blog/2014/09/10/president-obama-we-will-degrade-and-ultimately-destroy-isil.

11 Permanent Representative of Iraq to the UN, letter addressed to the President of the Security Council, UN Doc. S/2014/691, 20 September 2014. The Syrian government has not consented to the coalition's operations within its territory and has characterized them as a violation of its sovereignty and as unlawful. At the same time, the Syrian government has not actively opposed the coalition air strikes and has refrained from taking action against coalition aircraft in its airspace. See Permanent Representative of the Syrian Arab Republic to the UN, identical letters dated 16 September 2015 addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/718, 17 September 2015. The legality of the intervention in Syria has been discussed by other scholars, focusing specifically on Syria's “passive consent” and whether armed attacks carried out by a non-State actor can trigger a right of self-defence. See, for example, Gill, Terry D., “Classifying the Conflict in Syria”, International Law Studies, Vol. 92, 2016Google Scholar. Questions relating to jus ad bellum considerations will not be discussed in this article.

12 See, for example, Permanent Representative of Iraq to the UN, letter addressed to the President of the Security Council, UN Doc. S/2014/691, 20 September 2014. It was confirmed in Hamdan v. Rumsfeld, 548 U.S. 557 (2006), paras 67–69, that a conflict is non-international where a State is fighting non-State armed groups in States other than neighbouring countries (“transnational armed conflict”). The US Supreme Court held that the term “armed conflict not of an international character” “bears its literal meaning and is used … in contradistinction to a conflict between nations”.

13 International Criminal Tribunal for the former Yugoslavia (ICTY), The Prosecutor v. Tadić, Case No. ICTY-94-1-A, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, 2 October 1995, para. 70. The tribunal has confirmed and specified these criteria in later cases. See also ICTY, The Prosecutor v. Limaj, Case No. IT-03-66, Judgment (Trial Chamber), 30 November 2005.

14 ICTY, Tadić, above note 13, para. 70.

15 There are currently no widely accepted legal definitions of “terrorist” or “terrorism” under international law.

16 For a group to qualify as an organized armed group that can be a party to a conflict within the meaning of IHL, it needs to have a level of organization that allows it to carry out sustained acts of warfare and comply with IHL. Indicative elements were given in ICTY, The Prosecutor v. Haradinaj et al., Trial Judgment, 2008, para. 60. See also ICTY, The Prosecutor v. Boškoski and Tarčulovski, Trial Judgment, 2008, paras 199-203; ICTY, Limaj, above note 13, paras 94–134.

17 The contributions of members of the international coalition against IS are listed by country at: theglobalcoalition.org/en/partners/.

18 Article 19(2) of the Danish Constitution requires the consent of Parliament for the use of armed force “against any foreign State”. The paragraph is generally interpreted to mean that the government can repeatedly repel an armed attack but must seek the approval of Parliament for further defensive action. Despite its wording, the article has been invoked in a number of non-international armed conflicts.

19 Danish Parliament, Proposal for a Parliamentary Resolution on Danish Military Contribution in Support of Efforts in Iraq, B 122, 27 August 2014.

20 Danish Ministry of Defence, “The Effort against ISIL”, available at: www.fmn.dk/eng/allabout/Pages/the-effort-against-isil.aspx.

21 Ibid.

22 Ibid.

23 Ibid.

24 Ibid.

25 Ibid.

26 Lauterpacht, Hersch (ed.), International Law: A Treatise, Vol. 2: Disputes, War and Neutrality, Longmans, Green and Co, London, 1952, para. 293Google Scholar. Laws on neutrality are found in customary law as well as Hague Convention (V) respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land, 18 October 1907, and Hague Convention (XIII) concerning the Rights and Duties of Neutral Powers in Naval War, 18 October 1907.

27 This includes, according to Bothe, the engagement of military forces, massive financial support, the supply of any war material and the supply of military advisers to the armed forces of a party to the conflict. See Bothe, Michael, “The Law of Neutrality”, in Fleck, Dieter (ed.), The Handbook of International Humanitarian Law, 3rd ed., Oxford University Press, 2013Google Scholar.

28 H. Lauterpacht, above note 26, para. 312.

29 Ibid., para. 312.

30 M. Bothe, above note 27, p. 558.

31 Ferraro, Tristan, “The Applicability and Application of International Humanitarian Law to Multinational Forces”, International Review of the Red Cross, Vol. 95, No. 891/892, 2013CrossRefGoogle Scholar. In a more recent article, Ferraro looks at the legal position of the ICRC, which, according to Ferraro, also advocates a “support-based approach”. Accordingly, the ICRC considers that military or logistical support provided by third parties to one of the parties to a pre-existing non-international armed conflict can influence the application of IHL if it is considered as contributing to the collective conduct of hostilities or, in other words, can be “regarded as an integral part of the pre-existing conflict”. Ferraro, Tristan, “The ICRC's Legal Position on the Notion of Armed Conflict Involving Foreign Intervention and on Determining the IHL Applicable to This Type of Conflict”, International Review of the Red Cross, Vol. 97, No. 900, 2015CrossRefGoogle Scholar. Also see David Tuck and Cordula Droege, “Fighting Together and International Humanitarian Law: Setting the Legal Framework (1/2)”, October 2017, available at: https://blogs.icrc.org/law-and-policy/2017/10/12/fighting-together-international-humanitarian-law-setting-legal-framework-1-2/; David Tuck and Cordula Droege, “Fighting Together and International Humanitarian Law: Ensuring Respect for the Law and Assessing Responsibility for Violations (2/2)”, October 2017, available at: https://blogs.icrc.org/law-and-policy/2017/10/17/fighting-together-international-humanitarian-law-ensuring-respect-law-assessing-responsibility-violations-2-2/; David Tuck and Cordula Droege, “Fighting Together: Obligations and Opportunities in Partnered Warfare”, March 2017, available at: https://medium.com/law-and-policy/fighting-together-obligations-and-opportunities-in-partnered-warfare-362c9dfb741a.

32 See, for example, Dinstein, Yoram, War, Aggression and Self-Defense, Cambridge University Press, Cambridge, 2011, p 19CrossRefGoogle Scholar; Jan K. Kleffner, “Scope of Application of International Humanitarian Law”, in D. Fleck (ed), above note 27.

33 When common Article 3 is applicable, other rules of IHL of non-international armed conflict, including rules of conduct of hostilities, apply. See 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 (2016 Commentary on GC I), para. 389, available at: https://ihl-databases.icrc.org/ihl/full/GCi-commentary. See ICTY, Tadić, above note 13, paras 67, 69, 70; International Criminal Tribunal for Rwanda (ICTR), The Prosecutor v. Akayesu, Case No. ICTR-96-4-T, Judgment (Trial Chamber), 2 September 1998, paras 635–636; ICTY, The Prosecutor v. Kunarac, Kovač, and Voković, Case Nos IT-96-23 and IT-96-23/1-A, Judgment (Appeals Chamber), 12 June 2002, para. 57; Special Court for Sierra Leone, The Prosecutor v. Brima, Kamara and Kanu, Case No. SCSL 04-16-T, Judgment (Trial Chamber II), 20 June 2007, para. 245; International Criminal Court (ICC), The Prosecutor v. Lubanga Dyilo, Case No. ICC-01/04-1/06, Judgment (Trial Chamber I), 14 March 2012, para. 533. See also ICTY, The Prosecutor v. Blaškić, Case No. IT-95-14-T, Judgment (Trial Chamber), 3 March 2000, para. 64; ICTY, The Prosecutor v. Delalić, Case No. IT-96-21-T, Judgment (Trial Chamber), 16 November 1998, para. 209; ICTY, The Prosecutor v. Aleksovski, Case No. IT-95-14/1-T, Judgment (Appeals Chamber), 24 March 2000, para. 43–44. For a detailed analysis of the cases, see Lubell, Noam and Derejko, Nathan, “A Global Battlefield? Drones and the Geographical Scope of armed Conflict”, Journal of International Criminal Justice, Vol. 11, No. 1, 2013CrossRefGoogle Scholar.

34 This expansive view has been supported by a number of legal scholars. See N. Lubell and N. Derejko, above note 33; Schmitt, Michael N., “Charting the Legal Geography of Non-International Armed Conflict”, International Law Studies, Vol. 90, No. 1, 2014Google Scholar; Kretzmer, David, “Targeted Killings of Suspected Terrorists: Extra-Judicial Execution or Legitimate Means of Defence?” European Journal of International Law, Vol. 16, No. 2, 2005CrossRefGoogle Scholar; Arimatsu, Louise, “Territory, Boundaries and the Law of Armed Conflict”, Yearbook of International Humanitarian Law, Vol. 12, 2009CrossRefGoogle Scholar; J. K. Kleffner, above note 32; Sassóli, Marco, Transnational Armed Groups and IHL, Occasional Paper Series, No. 6, Program on Humanitarian Policy and Conflict Research, Harvard University, 2006Google Scholar.

35 The geographical scope of IHL may be subject to scrutiny by the ICC in the near future, if the investigation into the conflict in Afghanistan leads to the opening of a case on acts of ill-treatment of detainees allegedly committed since 2002 by the CIA in black sites in Poland, Romania and Lithuania, in connection with the armed conflict in Afghanistan. See: www.icc-cpi.int/afghanistan. For discussion on this, see Pothelet, Elvina, “War Crimes in Afghanistan and Beyond: Will the ICC Weigh In on the ‘Global Battlefield’ Debate?”, EJIL: Talk!, 9 November 2017Google Scholar, available at: www.ejiltalk.org/war-crimes-in-afghanistan-and-beyond-will-the-icc-weigh-in-on-the-global-battlefield-debate/; Coco, Antonio, “Freeing up the Rules on The Treatment of Detainees from the Debate on the Geographical Scope of International Humanitarian Law”, EJIL: Talk!, 3 January 2018Google Scholar, available at: www.ejiltalk.org/freeing-up-the-rules-on-the-treatment-of-detainees-from-the-debate-on-the-geographical-scope-of-international-humanitarian-law/. See also Clapham, Andrew, Gaeta, Paola and Sassóli, Marco (eds), The 1949 Geneva Conventions: A Commentary, 1st ed., Oxford University Press, Oxford, 2015, p. 77–83Google Scholar; Pejic, Jelena, “The Protective Scope of Common Article 3: More than Meets the Eye”, International Review of the Red Cross, Vol. 93, No. 881, 2011CrossRefGoogle Scholar.

36 Protocol Additional (I) 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 1987), Art. 1. See also Sandoz, Yves, Swinarski, Christophe and Zimmermann, Bruno (eds), Commentary on the Additional Protocols, ICRC, Geneva, 1987Google Scholar (ICRC Commentary on APs), paras 4489–4490: “The Protocol applies to all residents of the country engaged in a conflict …. Persons affected by the conflict within the meaning of this paragraph are covered by the Protocol wherever they are in the territory of the State engaged in conflict.”

37 Given the Geneva Conventions’ universal ratification, all non-international armed conflicts today are subject to common Article 3.

38 Melzer, Nils, Targeted Killing in International Law, Oxford University Press, Oxford, 2008, p. 258CrossRefGoogle Scholar: “The legislative novelty of Article 3 GC I to IV was that each contracting State established binding rules not only for its own conduct, but also for that of the involved non-State parties. The authority to do so derives from the contracting State's domestic legislative sovereignty, wherefore a territorial requirement was incorporated in Article 3 GC I to IV. This is not to say, however, that a conflict governed by Article 3 GC I to IV cannot take place on the territory of more than one contracting State. From the perspective of a newly drafted treaty text it appears more appropriate to interpret the phrase in question simply as emphasizing that Article 3 GC I to IV could apply only to conflicts taking place on the territory of States which had already become party to the new Conventions.” See also 2016 Commentary on GC I, above note 33, paras 115–120; A. Clapham, P. Gaeta and M. Sassóli, above note 35; Pejic, Jelena, “Extraterritorial Targeting by Means of Armed Drones: Some Legal Implications”, International Review of the Red Cross, Vol. 96, No. 893, 2014CrossRefGoogle Scholar; M. N. Schmitt, above note 34, pp. 11–12. See, however, Pictet, Jean (ed.), Commentary on the Geneva Conventions of 12 August 1949, Vol. 4: Geneva Convention relative to the Protection of Civilian Persons in Time of War, ICRC, Geneva, 1958Google Scholar (ICRC Commentary on GC IV), p. 36: “Speaking generally, it must be recognized that the conflicts referred to in Article 3 are armed conflicts, with armed forces on either side engaged in hostilities – conflicts, in short, which are in many respects similar to an international war, but take place within the confines of a single country.” See also ICTR, The Prosecutor v. Musema, Case No. ICTR-96-13-A, Judgment (Trial Chamber), 27 January 2000, paras 247–248, where the Tribunal found that a non-international armed conflict is one in which the “government of a single state [is] in conflict with one or more armed factions within its territory”. Note, however, that the ICTR Statute specifically includes violations committed in any neighbouring states within its jurisdiction, spelled out in Article 1.

39 AP II, Art. 1.

40 ICRC Commentary on GC IV, above note 38, p 50. For further description of the preparative works for GC IV, see A. Clapham, P. Gaeta and M. Sassóli, above note 35, pp. 79–83.

41 See discussed in J. Pejic, above note 35; Akande, Dapo, “Classification of Armed Conflicts: Relevant Legal Concepts”, in Wilmshurst, Elisabeth (ed.), International Law and the Classification of Conflicts, Oxford University Press, Oxford, 2012Google Scholar; Gleiss, Robin, “Armed Violence in Fragile States: Low-Intensity Conflicts, Spillover Conflicts, and Sporadic Law Enforcement Operations by Third Parties”, International Review of the Red Cross, Vol. 91, No. 873, 2009Google Scholar.

42 Referred to in A. Clapham, P. Gaeta and M. Sassóli, above note 35, p 82.

43 ICTR, Akayesu, above note 33, paras 608–609.

44 ICTY, Tadić, above note 13, para. 69. See also ICTR, Akayesu, above note 33, paras 635–636: “[The applicability of the rules is] irrespective of the exact location of the affected person in the territory of the State engaged in the conflict.” This approach is supported by conventional IHL: Geneva Conventions I and III, as well as Article 75 of AP I (rules related to arrest, detention and internment), apply to persons “related to the conflict”. See also 2016 Commentary on GC I, above note 33, paras 110, 124–126.

45 See also 2016 Commentary on GC I, above note 33, para. 460.

46 The question of extraterritorial application of Common Article 3 has given rise to a great deal of debate among legal scholars and practitioners. The debate shall not be repeated here, but it is important to point out that the ICRC has rejected “the notion that a person ‘carries’ a NIAC [non-international armed conflict] with him to the territory of a non-belligerent state” on the basis that “[i]t would have the effect of potentially expanding the application of rules on the conduct of hostilities to multiple states according to a person's movement around the world as long as he is directly participating in hostilities in relation to a specific NIAC”: ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, 2011, p. 22, available at: http://e-brief.icrc.org/wp-content/uploads/2016/08/4-international-humanitarian-law-and-the-challenges-of-contemporary-armed-conflicts.pdf. See also ICRC, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts, Geneva, 2015Google Scholar (2015 Challenges Report), available at: www.icrc.org/en/download/file/15061/32ic-report-on-ihl-and-challenges-of-armed-conflicts.pdf. See also 2016 Commentary on GC I, above note 33, paras 128–132. For a critique of this approach, see, e.g., M. N. Schmitt, above note 34; N. Lubell and N. Derejko, above note 33.

47 See T. Ferraro, “The Applicability and Application of International Humanitarian Law to Multinational Forces”, above note 31, p. 611; David Kretzmer, p. 195; M. N. Schmitt, above note 34, p. 16 on the ISAF operation in Afghanistan. See, however, the 2016 Commentary on GC I, above note 33, para. 473, in which the ICRC concludes that “[a]t the time of writing, there is insufficient identifiable State practice on its applicability in the territory of the home State”.

48 See also cases from the ICTY and the ICTR, in which the Courts find that IHL applies to the whole territory of the State affected by the conflict and cannot be limited to the battlefield: ICTY, Kunarac et al., above note 33, para. 57; ICTR, The Prosecutor v. Laurent Semanza, Case No. ICTR-97-20-T, Judgment (Trial Chamber), 15 May 2003, para. 367.

49 2015 Challenges Report, above note 46, p. 14. See also T. Ferraro, “The Applicability and Application of International Humanitarian Law to Multinational Forces”, above note 31, p. 611.

50 “The parties to the conflict must at all times distinguish between civilians and combatants. Attacks may only be directed against combatants. Attacks must not be directed against civilians.” 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, available at: ihl-databases.icrc.org/customary-ihl/eng/docs/home.

51 Melzer, Nils, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law, ICRC, Geneva, 2009 (ICRC Interpretive Guidance)Google Scholar.

52 This criterion caused some debate during the discussions on the Interpretive Guidance. See Schmitt, Michael N., “The Interpretive Guidance on the Notion of Direct Participation in Hostilities: A Critical Analysis” Harvard National Security Journal, Vol. 1, 5 May 2010Google Scholar.

53 ICRC Interpretive Guidance, above note 51, p. 50.

54 Ibid., p. 46.

55 For more information see Ibid., p. 44.

56 During the drafting of the Interpretive Guidance, a number of experts opposed the requirement that an organized armed group should belong to a party to the conflict in order to qualify as an armed force and found instead that the belligerent nexus criterion should “be framed in the alternative: an act in support or to the detriment of a party”. This understanding opens up to a broader application of the notion of direct participation in hostilities according to which persons who do not belong to or support one of the parties to the armed conflict could lose protection.

57 Schmitt, Michael (ed.), Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations, 2nd ed., Cambridge University Press, Cambridge, 2017, p. 378CrossRefGoogle Scholar. See also J. Pejic, above note 38.

58 ICRC Interpretive Guidance, above note 51, p. 65. According to Michael N. Schmitt, an alternative view popular among the group of experts discussing the Interpretative Guidance “looked instead to the chain of causation and argued that the period of participation should extend as far before and after a hostile action as a causal connection existed”: M. N. Schmitt, above note 52. According to this approach, any preparations causal to the act are considered direct participation, including, for example, the acquisition of materials, the construction of specific devices used for the attack, and their emplacement.

59 ICRC Interpretive Guidance, above note 51, p. 75. The same is reflected in Article 51(3) of AP I and customary law. See ICRC Customary Law Study, above note 50, Rule 6.

60 For example, see US Department of Defence, Law of War Manual, 2015, section 5.9. According to the Manual, the law of war as applied by the United States gives no “revolving door” protection, and considers that only when a direct participant has permanently ceased that participation will s/he regain protection, “because there would be no military necessity for attacking them”.

61 ICRC Interpretive Guidance, above note 51, p. 71.

62 Danish Ministry of Defence, Military Manual, September 2016, p. 144, available at: https://tinyurl.com/ydg959x7. An English translation of the Manual with be published in the beginning of 2019.

63 Ibid., p. 144.

64 See, for example, International Court of Justice (ICJ), Legality of the Threat of Use of Nuclear Weapons, Advisory Opinion, 8 July 1996, p. 226, paras 24–25; ICJ, Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion, 9 July 2004, para. 106. The applicability of human rights obligations during armed conflict is further confirmed by the presence of provisions for derogation in many human rights instruments, which allows States to derogate in times of war or public emergency.

65 It is debated whether non-State actors are also bound by human rights. See, for example, Clapham, Andrew, “Human Rights Obligations of Non-State Actors in Conflict Situations”, International Review of the Red Cross, Vol. 88, No. 863, 2006CrossRefGoogle Scholar.

66 The prohibition of arbitrary deprivation of life is a jus cogens principle and customary norm. Human Rights Committee, General Comment on Article 6, 114th Session, 2015; Human Rights Committee, General Comment 6, “Article 6 (Sixteenth Session, 1982)”, UN Doc. HRI/GEN/1/Rev.1, 1994, p. 6, para. 1.

67 ICRC Customary Law Study, above note 50, Rule 14.

68 See the United Nations Basic Principles on the Use of Force and Firearms by Law Enforcement Officials, Principle 9, adopted by UNGA Res. 45/166, 18 December 1999.

69 ICJ, Nuclear Weapons, above note 64; ICJ, Wall, above note 64; ICJ, Case Concerning Armed Activities on the Territory of the Congo (Democratic Republic of Congo v. Uganda), Judgment, 19 December 2005. See also Milanovic, Marco, “The Lost Origins of Lex Specialis: Rethinking the Relationship between Human Rights and International Humanitarian Law”, in Ohlin, Jens D. (ed.), Theoretical Boundaries of Armed Conflict and Human Rights, Cambridge University Press, Cambridge, 2015Google Scholar.

70 E.g. Inter-American Court of Human Rights, The Prosecutor v. Juan Carlos Abella, Series C, No. 11.137, Judgment, 18 November 1997, para. 161.

71 A selection of cases has been described in Melzer, Nils, Targeted Killing in International Law, 1st ed., Oxford University Press, Oxford, 2008CrossRefGoogle Scholar; Droege, Cordula, “Elective Affinities? Human Rights and Humanitarian Law”, International Review of the Red Cross, Vol. 90, No. 871, 2008CrossRefGoogle Scholar; Abresch, William, “A Human Rights Law of Internal Armed Conflict: The European Court of Human Rights in Chechnya”, European Journal of International Law, Vol. 16, No. 4, 2005CrossRefGoogle Scholar.

72 See European Court of Human Rights (ECtHR), McCann and Others v. United Kingdom, Appl. No. 18984/91, 27 September 1995, para. 194; ECtHR, Gül v. Turkey, Appl. No. 22676/93, 14 December 2000, para. 84; ECtHR, Gülec v. Turkey, Appl. No. 54/1997/838/1044, 27 July 1998, para. 67.

73 For more information, see ECtHR, Ergi v. Turkey, Appl. No. 23818/94, 28 July 1998; ECtHR, Akkum and Others v. Turkey, Appl. No. 21894/93, 24 March 2005; ECtHR, Akpinar amd Altun v. Turkey, Appl. No. 56760/00, 27 February 2007; ECtHR, Mansuroğlu v. Turkey, Appl. No. 43443/98, 26 February 2008; ECtHR, Özcan v. Turkey, Appl. No. 46221/99, 5 December 2005; ECtHR, Isayeva v. Russia, Appl. No. 57950/00, 24 February 2005; ECtHR, Bazorkina v. Russia, Appl. No. 69481/01, 27 July 2006.

74 C. Droege, above note 71, p. 532. The cases referred to are ECtHR, McCann, above note 72; ECtHR, Gül, above note 72; ECtHR, Ogur v. Turkey, Appl No. 21594/93, 20 May 1999; ECtHR, Hamiyet Kaplan v. Turkey, Appl. No. 36749/97, 13 September 2005; ECtHR, Ergi, above note 73; ECtHR, Özcan, above note 73; ECtHR, Isayeva, Yusupova and Bazayeva v. Russia, Appl. Nos 57947/00, 57948/00, 57949/00, 24 February 2005.

75 C. Droege, above note 71, p. 533.

76 Ibid.

77 See, for example, ECtHR, Kononov v. Latvia, Appl No. 36376/04, 17 May 2010; and ECtHR, Korbely v. Hungary, Appl. No. 9174/02, 19 September 2008, paras 86–94, in which the Court discussed the notion of direct participation in hostilities and hors de combat. See also analysis by W. Abresch, above note 71; Leach, Philip, “The Chechen Conflict: Analysing the Oversight of the European Court of Human Rights”, European Human Rights Law Review, No. 6, 2008Google Scholar; C. Droege, above note 71.

78 Combatant immunity implies that combatants remain protected from domestic prosecution for acts which, although in accordance with IHL, may constitute crimes under the national criminal law of the parties to the conflict. See ICRC Interpretive Guidance, above note 51, pp 83–84.

79 See Pictet, Jean (ed.), The Geneva Conventions of 12 August 1949: Commentary, Vol. 1: Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, ICRC, Geneva, 1952, p. 61Google Scholar; ICRC Commentary on APs, above note 36, p. 1359, para. 4489.

80 “Når der er grund til at antage, at den pågældende i udlandet vil deltage i aktiviteter, hvor dette kan indebære eller forøge en fare for statens sikkerhed, andre staters sikkerhed eller en væsentlig trussel mod den offentlige orden”: see Danish Aliens Act No. 1117, 2 October 2017, Art. 21(b), and Danish Law on Passports, Arts 1(2), 2(1)(4), 2(2–3) (Law No. 176 of 24 February 2015 Amending the Act on Passports to Danish Citizens, etc., the Aliens Act and the Code of Criminal Procedure (Strengthened Recruitment Against Armed Conflicts Abroad, etc.)).

81 Danish Law on Passports, Art. 2(b). Applied in two city court cases: City Court of Esbjerg, The Prosecutor v. Jakobsen, Case No. 31-2931/2016, 5 December 2016; and City Court of Copenhagen, The Prosecutor v. Palani, Case No. SS 2-30641/2015, 4 February 2015.

82 Danish Criminal Code, Act No. 977, 9 August 2017, Art. 101(a): “During an armed conflict to which Denmark is a party, anyone who has Danish citizenship or residency in the Danish State and who is affiliated with the enemy armed forces of a party to the armed conflict will be punished by imprisonment for up to ten years. Under particularly aggravating circumstances, the penalty may increase to life imprisonment. Direct participation in the conduct of hostilities is considered aggravating circumstances” (author's translation).

83 Ibid.

84 Ibid.

85 Parliamentary Report No. 44L, Prop. 44L (2015–2016), “Endringer i starffeloven mv. (militær virksomhet i væpnet konflikt m.m.)”.

86 Parliamentary Report No. 1556, Betænkning om Straffelovrådets udtalelse om visse spørgsmål vedrørende deltagelse i og hvervning til væbnede konflikter i udlandet, som den danske stat er part i, 2015. It is not explained in the report what is meant by “participation in an armed conflict”, but Danish counterterrorism legislation covers training, financing and recruiting for terrorism, public provocation, and incitement, as well as travelling for terrorism, in accordance with European Council Framework Decision 2002/475/JHA, 13 June 2002, amended in Decision 2008/919/JHA.

87 Danish Criminal Code, above note 82, Arts 114(c–e), 114(j) (Law No. 1880 of 28 December 2015 Amending the Criminal Code (Association for Hostile Armed Forces) and Law No. 642 of 8 June 2016 on the Amendment of the Criminal Code and the Repeal of the Law, which Prohibits the Danish Territory from Supporting War Crimes (Armed Conflicts Abroad, etc.)).

88 Framework Decision 2002/475/JHA, above note 86.

89 International Convention for the Suppression of Terrorist Bombings, No. 37517, 15 December 1997.

90 International Convention for the Suppression of the Financing of Terrorism, No. 38349, 9 December 1999. The Convention includes a slightly different wording to Article 19(2) of the Terrorist Bombings Convention.

91 Other conventions that include a similar clause to Article 19(2) of the Terrorist Bombings Convention are the 2005 International Convention for the Suppression of Acts of Nuclear Terrorism (Art. 4(2)), the 2010 Convention on the Suppression of Unlawful Acts relating to International Civil Aviation (Art. 6(2)), the consolidated text of the draft comprehensive convention (Report of the Ad Hoc Committee Established by General Assembly Resolution 51/210 of 17 December 1996, UN Doc. A/57/37, A/62/37, A/64/37, A/65/37, A/68/37; Report of the Coordinator on the Results of the Informal Consultations on a Draft Comprehensive Convention on International Terrorism, UN Doc. A/59/894; Report of the Working Group 6th Committee, UN Doc. A/C.6/60/L.6, A/C.6765/L.10; Summary Record of the 28th Meeting, UN Doc. A/C.6/69/SR.28 7). See also EU Council GA Doc. 6655/16, preamble § 19(a); LIBE Orientation Vote Doc. 11169/16, preamble § 6(b).

92 See discussions at the Danish Parliament, FT 2001/02, 2. saml., A843; FT 2001/02, 2. saml., B.1466.

93 Proposal by the United States on Art. 3 of the Terrorist Bombings Convention, first draft, 30 September 1997. The negotiations are reproduced in Carlos Fernando Diaz-Paniagua, “Negotiating Terrorism: The Negotiation Dynamics of Four UN Counter-Terrorism Treaties, 1997–2005”, PhD diss., City University of New York, 2008.

94 Proposals by Belgium, Syria, Pakistan, Argentina and New Zealand on Arts 1.4, 3, 5, 2bis, 10bis and 12ter, UN Doc. A/C.6/52/WG.1/CRP.11, 23 September 1997; by Belgium, China and Egypt on Art. 12ter, UN Doc. A/C.6/52/WG.1/CRP.28, 25 September 1997; and by Belgium on Art. 3, UN Doc. A/C.6/52/WG.1/CRP.39, 30 September 1997. The proposals are reprinted in UN General Assembly, Report of the Working Group on Measures to Eliminate International Terrorism, UN Doc. A/C.6/52/L.3, 3 October 1997, pp. 23–24. The negotiations are reproduced in C. F. Diaz-Paniagua, above note 93.

95 Sassóli, Marco, “Joint Series – Direct Participation in Hostilities: What Are the Issues and Where Are the Controversies?” ICRC Intercross Blog, 8 September 2014Google Scholar, available at: http://intercrossblog.icrc.org/blog/direct-participation-in-hostilities-what-are-the-issues-and-where-are-the-controversies; Stéphane Ojeda, “Global Counter-Terrorism Must Not Overlook the Rules of War”, ICRC Humanitarian Law and Policy Blog, 13 December 2016, available at: http://blogs.icrc.org/law-and-policy/2016/12/13/global-counter-terrorism-rules-war/. See also the discussion by the present author in Andersson, Anna, Høgestøl, Sofie A. E. and Lie, Anne Christine (eds), Fremmedkrigere: Forebygging, straffeforfølgning og rehabilitering i Skandiavia, Gyldendal, Copenhagen, 2018, p. 111–117Google Scholar.

96 For example, in Norwegian case law, see Oslo City Court, Case No. 09-200483MED-OTIR/03, 6 December 2010; in Swedish case law, see Gothenburg City Court, Case No. B 9086-15, 14 December 2015; Attunda City Court, Case No. B 4352-15, 15 February 2017; and in Belgian case law, see Antwerp City Court, Case No. FD35.98.47-12, 11 February 2015; Court of First Instance of Brussels, Case No. FD.35.98.212/11, 6 November 2015; The Turkish state v Fahriye Alptekin and 35 other Kurdish politicians, Case Nos FD.35.98.634/06, FD.35.98.502/07, FD.35.98.54/09 (Brussels City Court, 3 November 2016), FD.35.97.8-15 (Brussels City Court, 18 July 2016), FD35.98.374-14 (Brussels City Court, 27 January 2016), FD.35.97.15/12 (Court of Appeal of Brussels, 14 April 2016), FD.35.98.374-14 (Court of First Instance of Brussels, 27 January 2016), FD.35.97.15/12 (Court of Appeal of Brussels, 14 April 2016), FD.35.97.8-15 M. R. (Court of First Instance of Brussels, 18 July 2016). The Danish courts have not considered the applicability of Danish counterterrorism legislation in armed conflict directly (however, on indirect application, see, among others, Danish Supreme Court, Case No. U2009.1453H, 2009).

97 2016 Commentary on GC I, above note 33, para. 180.

98 Geneva Convention IV, Art. 33; AP I, Art. 51(2); AP II, Art. 13(2). See also ICTY, The Prosecutor v. Stanislav Galić, Case No. IT-98-29-T, Judgment (Trial Chamber), 5 December 2003, para. 56.

99 Law on the International Criminal Court, No. 342, 16 May 2001. Genocide is criminalized in the Law on Genocide, No. 132, 29 April 1955.

100 Danish Criminal Code, above note 82, Art. 21 (author's translation).

101 However, see ICRC Interpretive Guidance, above note 51, p. 55, according to which the temporal proximity of the inflicted harm does not influence the requirement of direct causation between the act and the harm inflicted.

102 The implications of the present state of the law, caused by the lack of regulation in non-international armed conflicts, have been discussed, among others, by S. Krähenmann, above note 4.