The role of a National court in implementing the European Union law and vulnerability of the principe of legal certainty

The ECJ Lucchini judgment is also analysed in the article as well as significance of its outcomes to the principle of res judicata in regard to the limitation of the latter. In the opinion of the author, this case does not raise the collision between legal certainty and a clear definition of res judicata, on the one side, and the supremacy and effectiveness of the EU law, on the other side. In this case the ECJ did not rely on the principles of effectiveness and equivalence, but it rather underlined the principle of supremacy and that state aid felt into the exclusive competence of the EU.