The ECJ (European Court of Justice) is the Institution which maintains observance of law in the interpretation and implementation of Community law. The EU law, as the law of a structure aiming at integration, is a law with a dynamic character which is being completed constantly. This dynamism and completion are related to fundamental rights and rule of law in the process of gaining democratic legitimacy. The European Communities, as Communities based on law, fill the gaps in the original texts of the founding Treaties by means of the Interpretations made by the ECJ. The ECJ basically realizes the aim of integration and meets the need of gaining democratic legitimacy of the European Communities.The candidate states which want to accede to the European Union are also required to adopt the values which gained the character of unwritten Union law by means of the judgments of the ECJ.