Wikipedia: European community law

The European Community is unique among international organizations in having a complex and highly developed system of internal law which has direct effect within the legal systems of its member states. There are three sources of Community law:

primary legislation: the treaties
secondary legislation: regulations, directives and decisions made by the Community institutions in accordance with the treaties
decisions of the European Court of Justice and the Court of First Instance

Primary Legislation: the treaties

The primary legislation, or treaties, function as in effect the constitutional law of the European Union. 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 ECSC Treaty of 1951
the EEC Treaty of 1957
the EURATOM Treaty of 1957
the Merger Treaty of 1961
the Acts of Accession of the United Kingdom, Ireland and Denmark (197x?)
the Budgetary Treaty of 1976(?)
the Acts of Accession of Spain, Portugal and Greece (197x?)
the Single European Act of 1985
the Treaty of Maastricht of 1991
the Acts of Accession of Austria, Sweden and Finland (199x?)
the Treaty of Amsterdam of 1997
the Treaty of Nice of 2001 (not yet ratified)

Secondary legislation: regulations, directives and decisions

Secondary legislation also includes interinstitutional agreements, which are agreements made between European Union institutions clarifing their respective powers, especially in budgetary matters. The Parliament, Comission and Council are capable of entering into such agreements.

The classification of legislative acts varies among the First, Second and Third Pillars.

In the case of the first pillar: Secondary legislation is classified based on to whom it is directed, and how it is to be implemented. Regulations and directives bind everyone, while decisions only affect the parties to whom they are addressed (which can be individuals, corporations, or member states). Regulations have direct effect, i.e. they are binding in and of themselves as part of national law, while directives require implementation by national legislation to be effective. However, states that fail or refuse to implement directives as part of national law can be fined by the European Court of Justice.

Specific topics in EC law