International law has long differentiated between international and non-international armed conflicts, traditionally regulating the former far more comprehensively than the latter. This is particularly stark in the case of detention, where the law of non-international armed conflict contains no rules on who may be detained, what processes must be provided to review their detention, and when they must be released. Given that non-international armed conflicts are now the most common form of conflict, this is especially worrying, and the consequences of this have been seen in the detention...