This is one of the most fundamental principles of EU law and it goes to the heart of much of the debate surrounding the intergovernmental / supranational nature of the EU. It also has significant importance for the concept of European governance.
The Court of Justice has through several decisions ruled that EU law has priority over national law both at the European and national Levels. In particular, the case of Costa vs. ENEL (1964) was instrumental in defining this legal principle.
In this case Mr Costa, an Italian citizen, refused to pay an electricity bill as he objected to a company that he had shares in, ENEL, being nationalised. He took the Italian government to the ECJ claiming that by nationalising ENEL they were ‘distorting the market’ something than ran counter to European law. The Italian government felt that only the Commission could challenge them in the European Courts and that Mr Costa had no recourse to challenge them using European law.
The EU ruled that in the European Courts Mr Costa did in fact have no legal recourse as the Commission was the only body that could challenge the Italian Government at a European Level.
However . . .
The ECJ also ruled that Mr Costa should be able to challenge the Italian Government in the Italian courts on a point of European law. In this situation European law would be have to take precedent over national law.
The ruling stated…
By creating a community of unlimited duration, having its own institutions, its own personality, its own legal capacity and capacity of representation on the international plane and, more particularly, real powers stemming from a limitation of sovereignty or a transfer of powers from the states to the community, the member states have limited their sovereign rights and have thus created a body of law which binds both their nationals and themselves.
It went on to say…
The law stemming from the treaty, an independent source of law, could not because of its special and original nature, be overridden by domestic legal provisions, however framed, without being deprived of its character as community law and without the legal basis of the community itself being called into question .
In essence this ruling said that unless EU law superseded national law the whole European legal system would be undermined and therefore decreed that when the two are in conflict EU law overrides national law.
It is important to remember that this is only in areas where states have chosen to give up sovereignty to the EU (in areas such as the single market, environment etc). You must remember that in nearly all non-community areas defence, taxation, social policy etc national courts remain sovereign.
You may like to revisit module two to remind yourself of the policy areas where states have given up some sovereignty and those where sovereignty is still retained.