1. Introduction While the definition and scope of the term “foreign terrorist fighter”(FTF) is controversial, in recent years it has been commonly used to refer to individuals who have travelled from their home states to other states to participate in or support terrorist acts, including in the context of armed conflict, especially in Iraq and Syria.7 Although FTF travel and return is not new, the dynamics of contemporary waves of travel and the extent and the nature of the responses on the national and international levels are. Normative, practical and political developments have unfolded internationally, regionally and nationally. The recognition of FTF flows as a threat to international peace and security, enshrined most notably in UN Security Council (UNSC) Resolution 2178 (2014) and under binding Chapter VII powers, put in place wide-reaching obligations on states to take all necessary and feasible measures to combat them. Subsequent international initiatives such as UNSC Resolution 2396 (2017), reiterated the characterization of FTFs, and in particular their return, as a grave threat to peace and security, and broadened states’ obligations to respond to its manifestations. UNSC Resolution 2178 (2014) requires states to prevent, disrupt, prosecute, rehabilitate and reintegrate FTFs and recognized the importance of “comprehensively addressing underlying factors, including by preventing radicalization to terrorism, stemming recruitment, inhibiting foreign terrorist fighter travel, disrupting financial support to foreign terrorist fighters, countering violent extremism, which can be conducive to terrorism, countering incitement to terrorist acts motivated by extremism or intolerance, promoting political and religious tolerance, economic development and social cohesion and inclusiveness, ending and resolving armed conflicts, and facilitating reintegration and rehabilitation…”.8 UNSC Resolution 2396 (2017) calls for additional action to be taken in the areas of border security and information sharing; judicial measures and co-operation; and prosecution, rehabilitation and reintegration strategies. In some areas, actions the UNSC has called for since 2014 have been applied selectively in practice, for example in relation to rehabilitation and reintegration of FTFs. On the other 7  For the controversies relating to the term, and associated human rights issues, see section 3.1 below. UNSC Resolution 2178 (2014), op. cit., note 1, describes FTFs 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”. Subsequent UNSC resolutions and legislative measures broadly adopted this language, whereas a broad range of research on the topic continues to refer to “foreign fighters” only rather than “foreign terrorist fighters”. Although, as noted below, the FTF term is problematic for its breadth and vagueness and the ensuing rights implications, it is the term most commonly used in the international arena and the one therefore used in this paper. 8  Preamble to UNSC Resolution 2178 (2014), para. 4, calls on states “to cooperate in efforts to address the threat posed by foreign terrorist fighters, including by preventing the radicalization to terrorism and recruitment of foreign terrorist fighters, including children, preventing foreign terrorist fighters from crossing their borders, disrupting and preventing financial support to foreign terrorist fighters, and developing and implementing prosecution, rehabilitation and reintegration strategies for returning foreign terrorist fighters”, op. cit., note 1. 8 Guidelines for Addressing the Threats and Challenges of “Foreign Terrorist Fighters”