Abstract Diplomatic immunity ratione materiae covers not official acts in general but merely acts performed in the exercise of diplomatic functions. Consequently, crimes in international law cannot be protected by this immunity because Article 3(1) of the Vienne Convention on Diplomatic Relations (vcdr) in general should accord with international law, although certain functions under the Article do not contain a 'legal' element. Further, diplomatic immunity ratione materiae cannot be upheld for jus cogens violations because Article 3(1) must not contradict a jus cogens prohibition. The dividing line between the procedural rule of immunity and the substantive rule of jus cogens is blurred by the fact that the scope of diplomatic immunity ratione materiae essentially hinges upon the contents a substantive treaty provision setting out diplomatic functions.