The children (and wives) of foreign ISIS fighters 81 power’ and States are thus free to act in accordance with their own national law and policy choices.55 In other words, the legal basis to detain, also preventively,56 in a NIAC cannot be found in IHL − which is nonetheless relevant as it provides an ‘inherent power to detain’57 and ‘conditions the authority to detain on compliance with procedural guarantees and humane treatment of detainees’ −58 but must rest elsewhere, principally in domestic law (either of the State that detains, in the case of Iraq, or of the State on whose territory the detention or internment occur, in the case of Syria). Since in NIACs, all detention issues fall within the sovereign interests of a single State, ‘domestic law applies to detention grounds and procedures as tempered by human rights law obligations’.59 Meaning, inter alia, that any deprivation of liberty, including internment,60 must be based on grounds established in law,61 in addition to being non-arbitrary ‘in a broader sense’62 and in line with existing treatment standards and procedural safeguards.63 In fact, the relevant rules of IHRL 55 ibid 50. Exceptionally, the authorization to detain may arise out of other branches of international law, eg it may be contained in United Nations Security Council Resolutions authorizing the use of force. See L Hill-Cawthorne, D Akande, ‘Does IHL Provide a Legal Basis for Detention in Non-International Armed Conflicts?’ EJIL: Talk! (7 May 2014) <www.ejiltalk.org/does-ihl-provide-a-legal-basis-for-detention-in-noninternational-armed-conflicts/>; commenting the famous judgment Serdar Mohammed v Ministry of Defence [2014] EWHC 1369 (QB). 56 Preventive security detention or ‘internment’ is defined as a deprivation of liberty ordered by the executive on the basis of future security threat without criminal charge. Hill-Cawthorne (n 54) 2. 57 ibid 107. As famously argued by Goodman ‘States have accepted more exacting obligations under IHL in international than in non-international armed conflicts. … [I]f States have authority to engage in particular practices in an international armed conflict [e.g. detention], they a fortiori possess the authority to undertake those practices in noninternational conflict’. Goodman (n 54) 50. 58 R Goodman, D Jinks, ‘International Law, U.S. War Powers, and the Global War on Terror’ (2005) 118 Harvard L Rev 2653, 2659-61. 59 G Rona, ‘International Law, Targeting, and Detention in the Age of International Terrorism’ Just Security (16 November 2015) 2 (emphasis added) <www.justsecurity.org/ 27674/international-law-targeting-detention-age-international-terrorism/>. 60 Hill-Cawthorne (n 54) 120-122. 61 HRC, ‘Concluding Observations: Trinidad and Tobago’, UN Doc CCPR/CO/70/TTO (10 November 2000) para 16; Medvedyev and others v France, App No 3394/03 (Judgment [GC], 29 March 2010) para 80. 62 Not to be equated with ‘against the law’, but interpreted more broadly to include elements of inappropriateness, injustice and lack of predictability. See HRC, Van Alphen v The Netherlands, UN Doc CCPR/C/39/D/305/1988 (15 August 1990) para 5.8. 63 Hill-Cawthorne (n 54) 116-133.