Relationship between EU law and national law in the context of case law of judicial bodies

The European Union requires its Member States to fulfil their commitments stemming from the membership in the EU responsibly and to assist in carrying out tasks flowing from the Treaties and to achieve the Union´s objectives in accordance with the principle of sincere cooperation. This scientific thesis points out the responsibility of Member States to fulfil their obligations in bona fide in accordance with principle pacta sunt servanda and it refers to well established case law of the Court of Justice of the EU clarifying the application primacy of EU law over national laws. At the same time it opens the discussion about decisions of constitutional courts related to the primacy of EU law in some EU Member States, in particular in Germany and Poland. This scientific thesis points out the significance of EU law in the process of further deepening of European integration and promoting rule of law values common to the EU Member States.