A fundamental judgment of the Court in respect of principles, the Costa v ENEL judgment shows that the EEC Treaty has created its own legal system which has become an integral part of the legal systems of the Member States, and that Community law takes precedence over national law.

In this judgment, the Court supplements the Stauder precedent by stating that respect for fundamental rights forms an integral part of the general principles of law protected by the Court of Justice and that the protection of such rights, whilst inspired by the constitutional traditions common to the Member States, must be ensured within the framework of the structure and objectives of the Community.

According to the Simmenthal judgment, the precedence of Community law applies even with regard to a subsequent national law.