ABSTRACT
The status of European Union (EU) law within the legal systems of the Member States is of fundamental importance, and there are a number of questions that must be answered before an understanding of Union law and its impact can be fully gained. Perhaps rather surprisingly, the founding Treaties did not directly address these questions and the Member States originally assumed that European Economic Community (EEC) law would have the same domestic effects as other sources of international law. This resulted in the status of the EEC Treaty being determined by each Member State’s own constitutional rules. The Court of Justice of the European Union took a different approach to the question of the impact of Union law and developed two principles, which later become known as the 'Twin Pillars upon which the Community rests', namely, supremacy and direct effect. Thus, the doctrine of the supremacy (or primacy) of Union law was established.
