The author discusses the relationship between two legal orders: international law and European Union (EU) law. The main provisions of this relationship have been established through the precedential practice of the Court of Justice of the European Union – the EU’s main judicial body. This kind of research seems important because of the gap in the theory of international law caused by the immutable dogma of the supremacy of international law. However, modern legal practice demonstrates a certain fragmentation of the international legal order because of the impact of the existence and development of regional supranational legal orders. The EU legal order, with its own special nature (sui generis), is undoubtedly one of the most developed among them. The Court of Justice of the European Union performs a crucial role in the EU legal system concerning application and interpretation of EU law. It provides a uniform interpretation of this law for the purposes of development of supranational integration. In this context the Court of Justice the European Union establishes the status of European law and its relationship with the national legal systems and international law. The Court acts as protector of the EU legal order against the influence of other legal orders. The Court’s precedential practice reveals EU law’s tendency towards its constitutionalization and the development of its autonomy. The latest practice indicates the Court’s powers to review the EU institutions’ acts in relation to the implementation of UN Security Council resolutions. This proves the Court’s ability to establish indirect control even over UN acts.