The Role of European Court of Justice in the Development of EU Legal Integration

European Court of Justice (ECJ) is the judicial body of the European Union (EU). Since its founding in 1952, ECJ has always played a prominent role in the development of the EU law. What has been studied in this article is the role of ECJ in transition of the EU law from duality (between national law of member states and EU law) to legal monism with the superiority of EU law. In implementation of its effective role, the ECJ has utilized different instruments such as Interpretation of EU law under the preliminary rulings, addressing the infringements of the EU law, recognizing the general principles of law in the form of case law, and also the principle of proportionality of regulations and domestic politics to promote the position of EU law in relation to municipal law of member states. This research partly reveals the process of EU legal integration, through the study of the ECJ case law.