to prosecution under some (but not all) domestic laws,77 IHL encourages amnesty at the end of the conflict for participation in conflict that has not violated IHL, to facilitate the termination of conflict and incentivize compliance with IHL.78 The obligation to prosecute FTFs should be read consistently with these principles. If an individual is designated a “foreign terrorist fighter” in the context of a conflict, this must be based on engagement in acts of terrorism that may constitute war crimes under IHL.79 The uncertainty about the definition and scope of the term “foreign terrorist fighter” covered by the UNSC resolutions, and related measures, mean that states have difficult policy decisions to make. Despite common perceptions to the contrary, FTF-related laws and policies are not limited to the groups referred to in UNSC resolutions (so-called “Islamic State”, the Al Nusrah Front and groups associated with Al-Qaida)80 or even, as noted above, to other designated terrorist groups. Instead, they often cover both travel to support a terrorist cause and travel to support armed groups that may resist a terrorist cause, and respect IHL. Where individuals who have fought against repressive regimes or against terrorist organizations such as the so-called “Islamic State” (in other words in line with the position and engagement of some prosecuting states), it has provoked serious controversy and policy debate concerning the public interest and the interests of justice in pursuing such prosecutions.81 While practice is far from established, there are implications for legal certainty and foreseeability, as well as respect for IHL, of the failure to distinguish “terrorist fighting” from participation in armed conflict, while abiding by IHL. 77  S. Krähenmann, “The Obligations under International Law of the Foreign Fighter’s State of Nationality or Habitual Residence, State of Transit and State of Destination” in FFILB, pp. 229-258, op. cit., note 14. 78  Customary International Humanitarian Law: Volume I: Rules, (Cambridge: Cambridge University Press & ICRC, 2009), <www.icrc.org/eng/assets/files/other/customary-international-humanitarian-law-i-icrc-eng.pdf>. See: Rule 159: “At the end of hostilities, the authorities in power must endeavour to grant the broadest possible amnesty to persons who have participated in a non-international armed conflict, or those deprived of their liberty for reasons related to the armed conflict, with the exception of persons suspected of, accused of or sentenced for war crimes.” 79  Both Additional Protocols to the Geneva Conventions prohibit, for example, “[a]cts or threats of violence the primary purpose of which is to spread terror among the civilian population”. See Article 51 (2), “Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I)”, 8 June 1977; and Article 13 (2), “Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts (Protocol II)”, 8 June 1977. 80  For example, UNSC Resolution 2249 (2015). 81  Questions have arisen regarding the legitimacy and appropriateness of prosecutions in various contexts, including in Belgium, the Netherlands and Denmark of returnees who had fought against ISIL. In 2017, Belgian courts ruled that individuals could not be prosecuted for “terrorism” in respect of acts that involved engagement in a “conflict”, though a higher court has paved the way for some prosecutions to proceed. For other cases see: L. Whyte, “Danish woman who fought against Isis faces jail sentence”, the Guardian, 19 December 2016, <www.theguardian.com/world/2016/dec/19/danish-woman-who-fought-against-isis-faces-jail-sentence>; “­Netherlands drops case against man suspected of killing Isis fighters”, the Guardian, 21 June 2016, <www. theguardian.com/world/2016/jun/21/netherlands-drops-case-against-man-suspected-of-killing-isis-fighters>; L. Dearden, “Danish woman faces jail after violating travel ban for fighting against Isis with Kurdish groups in Syria and Iraq”, the Independent, 13 December 2016, <www.independent.co.uk/news/world/europe/joanna-palani-danish-kurdish-woman-ypg-peshmerga-iraq-syria-fighting-isis-faces-jail-passport-police-a7471266.html>. Guidelines for Addressing the Threats and Challenges of “Foreign Terrorist Fighters” 25