The status of the law of the European Union has a significant meaning in the legal systems of the member states. The main tasks of this article are to understand the way the law of the European Union is being implemented and used on the territory of member states and to determine which of the “levels” of the law will have the priority in case of the conflict between the legal norms of the European Union and the national law In the article there is explained the difference between legal systems of member states what leads to the different status of the law of the European Union in these countries. Further on the author points out major principles in this sphere: direct action and supremacy, which were produced by the European Court. These two principles are then carefully elaborated by the author and their development and different aspects, such as the effectiveness of the law of the European Communities, are analyzed. Author illustrates his point of view on different examples and there are many references to the cases of the European Court in this respect. This helps to provide a broader basis for analysis of the issues touched upon in the article In the conclusion the author states that although the mentioned principles may be very simple and obvious, they continue to play an important role in the development of the European Community, thus increasing the significance of the law of the European Union, what in its turn provides its unified implementation on the territory of member-states.