The question of the relationship between international law and national law is one of the classic questions of constitutional law, but also arises in the European Union according to the ratio Union law-international law or in regard to the position of international law in the Union. The basic existence of an EU competence to conclude international agreements arises on the one hand, from the few explicit contractual basis. The EU concluded contracts Priority is given to before the secondary legislation, as they are under Article 216 paragraph 2 Treaty on the Functioning of the European Union (TFEU), inter alia binding on the Union's institutions. The chapter is in German.  Keywords: des Vlkerrechts, EU-Mitgliedschaft