EU law is based on the principle of its primacy. It is argued that by voluntarily acceding to the EU, the Member States agreed to limit their sovereignty and to transfer certain powers to the EU. Such principles were undisputed as long as they concerned the interpretation and application of EU secondary law concerning specific rights and obligations that should take their full effect in every Member State. From this perspective, the autonomous and uniform interpretation of EU law seems to be fully accepted.
Over the years, the EU took the stance that not only does EU law takes precedence over the national laws of the Member States, but cannot be repealed even by the constitutional systems of the Member States. The CJEU ruled that where the constitutional systems of the Member States collide with EU law, the national courts should not rely on the respective provisions of constitutional law.
This stance prompted a reaction from national constitutional courts. Examples can be found of decisions that clearly refuse the interference of EU law with elementary principles and values that form the core of their constitutional system. It is to be noted that they did so without generally refusing the primacy of EU law, and reserved the right to review the interpretation provided by the CJEU in exceptional circumstances where fundamental constitutional principles are at stake.
The debate became more heated when it moved from a strictly legal (jurisdictional) perspective. Recently, by relying on the primacy of EU law, EU institutions have begun to interfere with decisions taken by the Member States (especially Poland and Hungary) that clearly fall outside the scope of EU competences. They did so by relying on Articles 1, 2 and 19 TEU. Should such interpretation of the powers of the EU be confirmed, it would lead to the ability of the EU to control any political decision of its Member States.