Unlike the law of peace, which defines the areas where States may act or must refrain from acting by reference to a right of jurisdiction, international humanitarian law (IHL) sometimes assigns right and duties on the basis of de facto control over areas and persons. The responsibility of the occupying power, the right to enforce a blockade, the right to control humanitarian relief operations, and the right and duties of a non-state party to an Additional Protocol II type conflict are prime examples of such situations. The fact of control also matters where the issue is control over the conduct of a person. For instance, de facto control over troops determines the scope of the responsibility of a commander. By analysing those situations, the author highlights the relevance of facts under IHL and demonstrates that appropriate legal restraints on warfare must be based on the realities of a situation of war.