The thesis is based on one of Italy's arguments in the proceedings before the International Court of Justice in the Jurisdictional Immunities case against Germany. The ICJ issued its Judgment recently on February 3rd, 2012. One of Italy's arguments to deny Germany jurisdictional immunity before national courts was that the crimes committed by Nazi Germany between 1943 and 1945 on Italian territory amounted to breaches of jus cogens, and thus entailed an obligation to make reparation with the same character as the breached obligation, i.e. jus cogens character. Since the International Court of Justice did not rule on the question of the legal character of the reparation obligation following a breach of jus cogens, and since the question is, in the actual state of international law, still open in the view of the author, this thesis aims to take a closer view on the question. It discusses the question if jus cogens is more of a natural law character or more of a constitutional law character. Moreover, it discusses arguments such as the "waiver right" of an injured State, the necessary link between the specific obligation breached and the following content of the reparation obligation, the classical law on State responsibility as well as the distinction between "primary" and "secondary" obligation.