This paper explores the boundaries of international cooperation in criminal matters with respect to the German Constitution. The paper argues that a critical observation of developments in international cooperation in criminal matters is advisable. Cooperation in itself is not a guarantee for the protection of human rights. The guaranteed standard in the involved legal orders should be carefully studied and compared, before competences are “outsourced” to other international legal bodies. With respect to the German legal order, it is especially the guilt principle that raises concerns vis-à-vis other international legal orders.