jus cogens

noun | \ -ˈkä-gənz, -ˈkō-gens \ | jus co·gens
  1. : a principle of international law that is based on values taken to be fundamental to the international community and that cannot be set aside (as by treaty) it is doubtful that any state has ever violated jus cogens norms on a scale rivaling that of the Third Reich —Princz v. Federal Republic of Germany, 26 F.3d 1166 (1994) genocide and slave trade are violations of jus cogens