to sustainable long-term security.175 It may even be counter-productive if the exclusion forces individuals to remain in or revert to conflict zones, or in contexts in which terrorism and violent extremism can thrive. In this case, “risk exportation” by exclusion would appear to be incompatible with the obligations under UNSC Resolution 2178 (2014), which requires states to co-operate with each other to address the threats of FTFs.176 Deprivation of Liberty and Restrictions on Freedom of Movement Travel bans and revocation of passports are two of the methods of choice employed by states in respect to FTFs.177 While travel can be restricted to prevent acts of terrorism, for example, the nature of some travel restrictions has been criticized for being so broad as to be arbitrary and disproportionate.178 International law grants everyone the right to leave any country, including their own. According to Article 12 of the ICCPR, this right shall not be subject to any restrictions other than those that are provided by law and are necessary to achieve one of the legitimate aims specifically referred to in this provision, such as the protection of national security.179 Therefore, restrictions on the right to leave a country must also comply with the principles of legality, necessity and proportionality.180 Detaining an individual where there is a perceived risk of the individual travelling for a terrorist purpose, or upon return if not connected to the prosecution of a criminal offence, also raises serious human rights issues. Any deprivation of liberty must have a lawful basis. This is reflected in the ICCPR’s prohibition of “arbitrary detention”.181 Procedural safeguards must be provided immediately upon detention, including the right to challenge the lawfulness of one’s detention promptly before a judge. So-called preventive or administrative detention (detention on security grounds without criminal charges) of persons perceived to constitute a terrorist threat has been held to 175  See report of the UK Independent Reviewer of Terrorism Legislation, D. Anderson, “Shielding the Compass: How to Fight Terrorism without Defeating the Law”, op. cit., note 124; see also R. Bauböck and V. Paskalev, “Citizenship Deprivation A Normative Analysis”, March 2015, <www.ceps.eu/publications/ citizenship-deprivation-normative-analysis>. 176  See the argument developed in G. Goodwin Gil, “‘Temporary Exclusion Orders’ and their Implications for the United Kingdom’s International Legal Obligations, Part II”, 9 December 2014, <www.ejiltalk.org/temporary-exclusion-orders-and-their-implications-for-the-united-kingdoms-international-legal-obligations-part-ii/>. 177  “‘Foreign Terrorist Fighter’ Laws, Human Rights Rollbacks Under UN Security Council Resolution 2178”, Human Rights Watch, op. cit., note 130 cites countries that have enacted travel bans as including Austria, Azerbaijan, Belgium, Denmark, France, Italy, the Netherlands, Tajikistan, the United Kingdom and a number of countries from outside of the OSCE area. 178  Ibid. 179  See also Article 2 of Protocol 4 to the ECHR. 180  For further considerations concerning freedom of movement see UN CTITF Guidance 2018, op. cit., note 10, pp. 15-20. 181  While Article 9 ICCPR prohibits arbitrary detention, Article 5 ECHR (Article 5) provides an exhaustive list of grounds of detention (e.g., pursuant to criminal charge or pending deportation) which do not include security detention. Guidelines for Addressing the Threats and Challenges of “Foreign Terrorist Fighters” 51