Recent events in the Middle East present the latest and undoubtedly not the last challenge to international engagement with armed non-state actors. Over the last many years international humanitarian law has increasingly regulated the behaviour of armed non-state actors with regard to the protection of civilians. At the same time, counter-terror measures have increasingly addressed such conduct, as well as controlled the extent to which other actors may interact with armed non-state actors. Yet there is a fundamental contradiction between these regulatory regimes. The report takes a case study approach to examine the conundrum facing policymakers and, not least, state militaries, when navigating these policy regimes in Iraq and Syria. It analyses two prominent armed non-state actors and their acceptance of these regulatory regimes the People´s Protection Units (YPG) and Islamic State. The report concludes that it is time to consider strategic interoperability of international humanitarian law and counter-terror regimes in order to maximise the protection of civilians. Drawing a line in the sand at compliance with international humanitarian law and forcing armed non-state actors to choose whether or not they stand with the "terrorists" (e.g. IS) can motivate many of them towards compliance (e.g. PKK/YPG and others such as Ahrar al-Sham), as long as counter-terror measures don´t undermine the incentives to do so.