European Union law (historically called European Community law) is a body of treaties, law and court judgements which operates alongside the legal systems of the European Union's member states. It has direct effect within the EU's member states and, where conflict occurs, takes precedence over national law.
The primary source of EU law is the EU's treaties. These are power-giving treaties which set broad policy goals and establish institutions that, amongst other things, can enact legislation in order to achieve those goals. The legislative acts of the EU come in two forms: regulations and directives. Regulations become law in all member states the moment they come into force, without the requirement for any implementing measures, and automatically override conflicting domestic provisions. Directives require member states to achieve a certain result while leaving them discretion as to how to achieve the result. The details of how they are to be implemented are left to member states.
EU legislation derives from decisions taken at the EU level, yet implementation largely occurs at a national level. The principle of uniformity is therefore a central theme in all decisions by the European Court of Justice, which aims to ensure the application and interpretation of EU laws does not differ between member states.
The development of law of the European Community has been largely moulded by the European Court of Justice (ECJ). In the landmark case of Van Gend en Loos in 1963, the ECJ ruled that the European Community, through the will of Member States expressed in the Treaty of Rome, "constitutes a new legal order of international law for the benefit of which the states have limited their sovereign rights albeit within limited fields."
The distinction between European Community (EC) law and European Union law is that based on the Treaty structure of the European Union. The European Community constitutes one of the 'three pillars' of the European Union and concerns the social and economic foundations of the single market. The second and the third pillars were created by the Treaty on European Union (the Maastricht Treaty) and involve Common Security and Defence Policy and Internal Security. Decision-making under the second and third pillars is not subject to majority voting at present. The Maastricht Treaty created the Justice and Home Affairs pillar as the third pillar. Subsequently, the Treaty of Amsterdam transferred the areas of illegal immigration, visas, asylum, and judicial co-operation to the European Community (the first pillar). Now Police and Judicial Co-operation in Criminal Matters is the third pillar. Justice and Home Affairs now refers both to the fields that have been transferred to the EC and the third pillar.
Several principles such as subsidiarity, proportionality, the principle of conferral, and the principle of legal certainty have become prominent in the development of European Union law. Scholars such as Catherine Barnard argue that the Four Freedoms form the substantive law of the EU: free movement of goods, services, capital, and labour within the internal market of the EU.
The primary legislation, or treaties, are effectively the constitutional law of the European Union. They are created by governments from all EU Member States acting by consensus. They lay down the basic policies of the Union, establish its institutional structure, legislative procedures, and the powers of the Union. The Treaties that make up the primary legislation include:
The various annexes and protocols attached to these Treaties are also considered a source of primary legislation.