The author deals in her paper with the development of the European Communities and the European Union in the broader context. She mainly focuses on the three-pillared structure of the European Union and the development of the Treaties, which constitute its basis. Three European Communities, i.e. the European Community, the European Coal and Steel Community and the European Atomic Energy Community, forming the first pillar of the European Union are based on a supranational cooperation. The supranational character of EC is especially demonstrated by the activity of its institutions and in the legislative process. The Common Foreign and Security Policy form the second pillar of the European Union and the Third Pillar comprises cooperation in the area of justice and home affairs, whose special feature is intergovernmental cooperation. In fact, it is a coordinated system of cooperation, since the powers in the mentioned areas were not transferred to the common institutions and Member States decide in the EU Council on the basis of unanimity.

Since the European Union is the economic and integration association of states, which has not legal personality under the international law, this chapter also deals with the legal status of European Communities and their legal personality under the international law. The European Union has its own institutional and legal system, but it operates only in scope and forms granted to it by all Member States