Jus cogens has become one of the most frequently used arguments in international law. Some authors ride roughshod over the traditional regimes, claiming that the effectiveness of jus cogens or obligations erga omnes must be the paramount consideration in any conceivable instances, even concerning their indirect repercussions. This book, the outgrowth of a joint reflection by French and German international lawyers, attempts to reconceptualize the doctrine of hierarchy in international law by emphasizing that a clear distinction should be drawn between primary rules, which encapsulate precepts for the protection of the basic values of the international community, and secondary rules, which determine the regime of legal consequences flowing from a breach of such rules of conduct. It will thus contribute to clarifying the true meaning of jus cogens and other similar concepts not only for the sake of academic determinacy, but also for such practical purposes as jurisdictional immunities.