Legal framework

War crimes—such as targeting civilians, torture, or the use of prohibited weapons—are grave breaches of the Geneva Conventions of 1949 and their Additional Protocol I, and other serious violations of the laws and customs of war. War crimes are punishable under international criminal law. All States have an obligation to prevent war crimes or punish them if they occur. 

More information and core legal documents can be found here: IHL treaties; Customary IHL.