Costa and the Primacy of Union Law

In cases brought before a national court in a European Union (EU) Member State, EU law must prevail over national law in the case of conflict. This simple idea goes under the name of the primacy of EU law, and is now generally recognised as an essential element of the EU legal order. The primacy rule, also often called the primacy principle, was not contained in the original Community Treaties and is still not contained in the current text of the EU Treaties. It was, rather, established by the European Court of Justice (ECJ), as a ‘product of judicial creativeness’. This was done in an early judgment of 1964, Costa v ENEL, which is the subject of this chapter. Following the general format of this volume, this chapter will successively discuss the historical and doctrinal context in which the Costa judgment arose (section II), the content of the judgment itself (section III), the reception of the primacy rule established in Costa by the national courts of the Member States (primarily those of Italy where the case originated) and by the national governments (section IV), and finally the further evolution of the primacy rule, which has been a frequent object of refinements and extensions in the 60 years since Costa (section V).