Customary international humanitarian law

Customary international law is made up of rules that come from "a general practice accepted as law" and that exist independent of treaty law. Customary international humanitarian law (IHL) is of crucial importance in today's armed conflicts because it fills gaps left by treaty law in both international and non-international conflicts and so strengthens the protection oered to victims.

International law comes from both treaty law and rules of what is known as customary international law. Treaties are written conventions in which States formally establish certain rules. Customary international law, on the other hand, is not written but derives from "a general practice accepted as law". To prove that a certain rule is customary, one has to show that it is reflected in state practice and that the international community believes that such practice is required as a matter of law.