International humanitarian law (IHL) is the set of rules designed to limit the human cost of armed conflict. It protects people who are not, or are no longer, directly participating in hostilities; and it restricts the methods and means of warfare. IHL also sets out mechanisms designed to ensure compliance with its rules, and to punish serious violations, which are also referred to as 'war crimes'. Under IHL, individuals are criminally responsible for the war crimes they commit. In addition, under IHL commanders and other superiors are criminally responsible for war crimes committed pursuant to their orders, as well as for war crimes committed by their subordinates when they fail to take adequate measures to prevent or punish those crimes. Customary IHL affirms the right of States to vest their courts with universal jurisdiction over war crimes, and requires them to exercise that jurisdiction where appropriate. In addition, the four Geneva Conventions of 1949 (GC I–IV), their Additional Protocol I of 1977 (AP I) and other treaties contain specific obligations regarding penal repression of serious violations of IHL.