C. Paulussen It is admitted that stripping of citizenship and thus the removal of the active nationality principle does not mean that investigation and prosecution of war crimes committed by one’s former nationals will never be possible. After all, Rule 157 of the same Customary International Humanitarian Law Study of the ICRC, Vol. 1: Rules clarifies that “States have the right to vest universal jurisdiction in their national courts over war crimes”.50 However, in practice, one can see that investigation and prosecution based on “pure” universal jurisdiction51 – especially after Belgium experienced the political consequences of such a broad law –52 are scarce, and that the exercise of universal jurisdiction has now often been made dependent on certain conditions. In the Netherlands, for example, the International Crimes Act of 2003 stipulates that universal jurisdiction for international crimes such as war crimes committed abroad is conditional upon the suspect’s presence in the Netherlands.53 Hence, if a Dutch foreign fighter’s citizenship is stripped, prosecution for war crimes may still be possible under universal jurisdiction, but only if that person is present in the Netherlands, which often will not be the case. It has therefore also been argued that the Netherlands should stop applying the measure of deprivation of nationality, for it undermines accountability efforts among other things, not only in the context of terrorist crimes, but also in the context of international crimes such as war crimes.54 Going further, the point could be made that if a state does not bring its foreign fighters to justice (either in its own courts or elsewhere), it will not only undermine the fight against impunity for crimes already committed, but also it may lead to a prolongation of the conflict,55 which, in turn, will lead to new international humanitarian law violations.56 50 J.-M. Henckaerts and L. Doswald-Beck, above note 46, p. 604. 51 “Pure universal jurisdiction takes place when a state asserts jurisdiction (either through an investigation or by seeking extradition) of a suspect who is not present in the state’s territory.” See International Center for Transitional Justice, Advancing Global Accountability: The Role of Universal Jurisdiction in Prosecuting International Crimes, December 2020, available at: https://www.ictj.org/sites/default/files/ICTJ_Report_ Universal_Jurisdiction.pdf, p. 13. 52 See e.g. S. R. Ratner, “Belgium’s War Crimes Statute: A Postmortem”, American Journal of International Law, Vol. 97, No. 4, 2003, pp. 888–897. 53 Netherlands International Crimes Act, 2003, Section 2, para. 1 (a). 54 See C. Paulussen, Reactie op het wetsvoorstel permanentmaking bevoegdheid tot intrekking Nederlanderschap in het belang van de nationale veiligheid (Keten-ID: 10430), 25 January 2021, available at: https://www.internetconsultatie.nl/intrekkingnederlanderschap/reactie/152199/bestand, pp. 4–6. 55 See also UN Security Council, “Preambular: ‘Concerned that foreign terrorist fighters increase the intensity, duration and intractability of conflicts’”, in Resolution 2178 (2014), S/RES/2178 (2014), 24 September 2014, available at: http://www.securitycouncilreport.org/atf/cf/%7B65BFCF9B-6D27-4E9C8CD3-CF6E4FF96FF9%7D/s_res_2178.pdf, p. 2. 56 See also Council of Europe Parliamentary Assembly, Withdrawing Nationality as a Measure to Combat Terrorism: a Human-rights Compatible Approach?, Resolution 2263 (2019), available at: http://assembly. coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fileid=25430&lang=en, para. 8: “The Assembly also notes that the practice of depriving of their nationality persons involved in terrorist activities (including “foreign fighters”) or suspected of such involvement may lead to the “exporting of risks”, as those persons may move to or remain in terrorist conflict zones outside Europe. Such a practice goes against the principle of international co-operation in combating terrorism, reaffirmed, inter alia, in UN Security Council Resolution 2178 (2014), which aims at preventing foreign fighters from leaving their State of residence or nationality, and may expose local populations to violations of international human rights and humanitarian law.” 616