The sharing of competence between EU and Member States is one of the crucial issues of international law and EU law. By a clear reading of Treaty articles, it can be understood that the EU was created by founders with a limitation of sovereignty or a transfer of powers stemming from the states to EU. EU makes a different claim for its sovereignty and competence by way of original doctrines and principles created the ECJ. By reason of deepening and diffusing of integration in all areas the autonomy and validity of this new legal order have been gradually contravened by the Member States’ courts. The issue of conflict of competence and, more importantly, the issue of who will make a decision in a case of conflict created a crucial uncertainty which affected competence order between EU and Member States and citizen’s rights. It will be extremely difficult to use the theory of law as a tool because of political nature of deepening process of integration. The approach that tries to solve the competence issues by law engineering will has to re-produce new solutions in each time, as political players, which they are also political engineer, will change the factors of the issue.