Case 6/64 Costa v ENEL

Case 6/64 Costa v ENEL established that European Union law takes precedence over conflicting national laws within member states. The European Court of Justice ruled that when there is a conflict between EU rules and a country's laws, the EU rules override the national laws. This decision solidified the principle of supremacy of EU law, ensuring that EU regulations are uniformly applied and prioritized across all member states, promoting legal consistency and integration within the EU.