Stripping foreign fighters of their citizenship: International human rights and humanitarian law considerations 1980 to challenge the Soviet occupation of that country, and, more recently, the British national Mohammed Emwazi, better known as “Jihadi John”, who in 2012 travelled to Syria to join the Islamic State of Iraq and Syria (ISIS) and who would become one of the terrorist organization’s most infamous executioners.2 Notably the conflict in Syria and Iraq has attracted an unprecedented number of foreign fighters: on 28 November 2017, Vladimir Voronkov, Under-Secretary-General of the United Nations (UN) and Head of its Office of Counter-Terrorism, briefed the UN Security Council and “said that, at one stage more than 40,000 foreign terrorist fighters from 110 countries might have travelled to join the conflict in Syria and Iraq”.3 Indeed, many of these foreign fighters joined terrorist groups, such as al-Nusra or ISIS, which is why the attention quickly moved from foreign fighters as such to foreign terrorist fighters (FTFs), defined by the UN Security Council as “individuals who travel to a State other than their States of residence or nationality for the purpose of the perpetration, planning, or preparation of, or participation in, terrorist acts or the providing or receiving of terrorist training, including in connection with armed conflict”.4 In responding to the foreign fighter and especially the FTF phenomenon and the groups that they have joined, states, and international and regional organizations have implemented a broad set of measures, from a full-out military campaign,5 to criminal6 and administrative measures.7 It is interesting to note that in the context of criminal law, the focus has recently shifted from the initial limited counterterrorism perspective – with foreign fighters being mainly prosecuted for membership of a terrorist organization – to broader charges, showing the realization that foreign fighters can also commit crimes as individuals participating in hostilities, such as war crimes.8 But as the standards of criminal law may be difficult to meet, especially in view of the difficulty of securing evidence in (post-) conflict situations, states have increasingly resorted to administrative measures. One of these is citizenship stripping or deprivation of 2 3 4 5 6 7 8 See more generally N. Arielli, From Byron to bin Laden: A History of Foreign War Volunteers, Harvard University Press, Cambridge, MA, 2018. UN Security Council, 8116th Meeting (PM), Greater Cooperation Needed to Tackle Danger Posed by Returning Foreign Fighters, Head of Counter-Terrorism Office Tells Security Council, SC/13097, 28 November 2017, available at: https://www.un.org/press/en/2017/sc13097.doc.htm (all internet references were accessed in July 2021). UN Security Council, “Preambular”, in Resolution 2178 (2014), S/RES/2178 (2014), 24 September 2014, available at: http://www.securitycouncilreport.org/atf/cf/%7B65BFCF9B-6D27-4E9C-8CD3-CF6E4FF96FF9% 7D/s_res_2178.pdf, p. 2. See Operation Inherent Resolve, available at: https://www.inherentresolve.mil/About-CJTF-OIR/. See C. Paulussen and K. Pitcher, “Prosecuting (Potential) Foreign Fighters: Legislative and Practical Challenges”, ICCT Research Paper, January 2018, available at: https://icct.nl/app/uploads/2018/01/ICCTPaulussen-Pitcher-Prosecuting-Potential-Foreign-Fighters-Legislative-Practical-Challenges-Jan2018.pdf. See B. Boutin, “Administrative Measures against Foreign Fighters: In Search of Limits and Safeguards”, ICCT Research Paper, December 2016, available at: https://icct.nl/app/uploads/2016/12/ICCT-BoutinAdministrative-Measures-December2016-1.pdf. For further information on cumulative prosecution of foreign fighters, see the article by Hanne Cuyckens, “Foreign Fighters and the Tension Between Counterterrorism and International Humanitarian Law: A Case for Cumulative Prosecution Where Possible”, in this issue of the International Review of the Red Cross. 607