This article examines several questions relating to international humanitarian law (jus in bello) with respect to the conflicts against the Islamic State. The first question explored is the classification of conflicts against the Islamic State and the relevant applicable law. The situation in Iraq is a rather classic non-international armed conflict between a state and a non-state actor with third states intervening alongside governmental forces. The situation in Syria is more controversial, especially with respect to the coalition's airstrikes against the Islamic State on Syrian territory. If the Syrian government is considered as not having consented to the coalition's operations, then, according to this author's view, the coalition is involved in two distinct armed conflicts: an international armed conflict with the Syrian government and a non-international armed conflict with the Islamic State. The second question analyzed in the article bears on the geographical scope of application of international humanitarian law. In this context, the article examines whether humanitarian law applies: in the entire territory of the state in whose territory the hostilities take place, in the territories of the intervening states, and in the territory of a third state.