national security, it was also accepted that the applicants could not be deported “for the time being” (Judgement of 19/02/2009, No. 3455/05, § 170). Following the terrorist attacks in September 2001, the applicants were detained as suspected international terrorists and it was believed that their presence at liberty in the United Kingdom gave rise to a threat to national security. Given that they could not be deported because they would be at risk of ill-treatment, each of the applicants was detained. The Court held that as there was no specific foreseeable time frame in which deportations could take place. Consequently, the detention of the applicants was unlawful (ibid at § 170). Whenever the applicant is already detained and it becomes clear during such detention that a readmission will not be possible, the detention order has to be lifted without undue delay. In Suso Musa v. Malta, the applicant was held in detention until March 2013 despite the fact that the authorities had known since 11 February 2013 that there was no prospect of returning him ( Judgement of 23/07/2013, No. 42337/12, § 104). The Court held that there was a violation of Article 5 (1) (f) because the detention order should have been lifted immediately after it became known that a readmission would not be possible. ii. Requirement of Active Steps for Removal The Court has reiterated many times that States must take active steps to remove the specific individual from the territory as quickly as possible when someone is deprived of their liberty in order for the detention to be lawful. Even though these steps do not need to be of a specific formal nature, they have to be undertaken with adequate determination and due diligence (X. v. Switzerland, Commission decision of 9 December 1980). In Feilazoo v. Malta, the Court also held that the applicant’s detention was not lawful under Article 5 (1) ECHR, as it lasted for fourteen months and the authorities were aware that the deportation was not feasible and failed to pursue the matter with diligence (Judgement of 11/03/2021, No. 6865/19, §§ 101-104). The Maltese authorities were aware that there was no prospect of readmission because the Nigerian authorities had doubts as to the applicant’s identity (Ibid at §§ 107-110). The only step that the authorities took within a 14-month period was to contact the Nigerian authorities for the issuing of a passport. The Court did not consider this request a sufficient step. The Court has gone on to clarify additional requirements for detaining people under the second limb of Article 5(1)(f). First, steps towards deportation must concern the individual applicant rather than a general group.100 Second, such steps have to be taken with “energy and impetus”.101 Finally, the undertaken steps must be continuous. Whenever such steps are not taken with due diligence, the detention will cease to be permissible.102 D. Detention Practices on Kos All arrivals to the Aegean islands are subjected to a ‘geographical restriction’ that prohibits movement outside the island to which they are assigned until the conclusion of their asylum procedure. At the same time, the Kos detention scheme is distinctive. It is currently the only island among the five Aegean EU Hotspots to have a functioning Closed Reception Facility: for asylum seekers on Kos, the experience of detention is therefore intertwined with the unique challenges of arriving via the islands. 100 ECtHR, Judgement of 19/02/2009, No. 3455/05, A. and Others v. U.K., para 167. 101 ECtHR, Judgement of 19/05/2016, No. 37289/12, J.N. v. the United Kingdom, para 107. 102 ECtHR, Judgement of 23/07/2013, No. 42337/12, Suso Musa v. Malta, para 91, ECtHR, Judgement of 15/12/2016, No. 16483/12, Khlaifia and Others v. Italy [GC] para 90, ECtHR, Judgement of 19/02/2009, No. 3455/05, A. and Others v. the United Kingdom [GC], para 164, ECtHR, Judgement of 12/02/2013, No. 58149/08, Amie and Others v. Bulgaria, para 72, ECtHR, Judgement of 19/04/2021, Nos. 56751/16, 33762/17, Shiksaitov v. Slovakia, para 56, with further examples of cases disclosing a violation of that provision. 13 DETENTION OF MIGRANTS ON THE ISLAND OF KOS