Costa v ENEL

Costa v ENEL was a 1964 decision of the Court of Justice of the European Communities holding that European Community law takes precedence over the conflicting national law of member states, including national law enacted after the relevant Community provisions, because member states had permanently limited their own sovereign rights by joining the Community and could not unilaterally override the obligations they had accepted. The case arose from an Italian citizen's challenge to the nationalization of the electricity industry. It established the doctrine of the supremacy of European Union law over national law.