The EU legislative process largely involves the Council of the European Union and the European Parliament. However, the European Commission and other EU organs are also involved. For a detailed overview of the legislative process, see the EU guide to ordinary legislative procedure.

According to the European Commission, legislation is divided into two classes:

• Primary legislation consists of treaties between EU member countries. They set out EU objectives, rules for EU institutions, how decisions are made and the relationship between the EU and its member countries. Every action taken by the EU is founded on treaties. Treaties are comparable to constitutional law in many countries. 
• Secondary legislation consists of regulations, directives, decisions, recommendations, and opinions which are used to implement the policies set out in the treaties. 

Treaties are the European Union’s primary legislation, comparable to constitutional law in many countries.  They establish the fundamental features of the Union, in particular the responsibilities of decision-making bodies and legislative procedures. Treaties are negotiated between representatives of member states but must be be ratified, either by national parliaments or via citizen referendum. Below are some major treaties in EU history along with their accompanying legal citations.

• Treaty Establishing the European Coal and Steel Community (1951) (E.C.S.C. Treaty), 261 U.N.T.S. 140
• Treaty Establishing the European Atomic Energy Community (1957) (Euratom Treaty), 298 U.N.T.S. 167
• Treaty Establishing the European Economic Community (1957) (Treaty of Rome or the E.E.C. Treaty), 298 U.N.T.S. 11
• Treaty Establishing a Single Council and a Single Commission of the European Communities (1965) (the Merger Treaty), 1965 J.O. (152) 1
• Single European Act (1986), 1987 O.J. (L 169) 1
• Treaty on European Union (1992) (consolidated version), 2012 O.J. C326/13
• Treaty of Amsterdam (1997), 1997 O.J. C340/1
• Treaty of Nice (2001), 2001 O.J. (C 80) 1
• Treaty of Lisbon (2007), 2007 O.J. (C306) 1
• Treaty on the Functioning of the European Union (2007) (consolidated version), 2012 O.J. C326/47

The Official Journal (OJ) is the official gazette of the European Union. It contains the texts of secondary legislation, draft legislation and official announcements from EU institutions. It is published in two sections: Legislation (L series) and Information and Notices (C series). 

Legislation (L Series)

This series contains the texts of all secondary legislation. The texts can take several forms: 

• Regulations are binding legislative acts which apply directly to all member states. They often concern trade issues.
• Directives are legislative acts that set out goals which all EU countries must achieve. However, it is up to the individual countries to devise their own laws on how to reach these goals.
• Decisions are binding on those to whom it is addressed (e.g. an EU country or an individual company) and are directly applicable.
• Recommendations allow EU institutions to make their views known and to suggest a line of action without imposing any legal obligation on those to whom it is addressed. They are not legally binding.
• Opinions are issued by the main EU institutions (Commission, Council, Parliament), the Committee of the Regions and the European Economic and Social Committee. They are not legally binding. 

Information and Notices (C Series)

This series contains:

• Information about current activities of the institutions, which includes questions and answers in the European Parliament and actions before the Court of Justice.
• Announcements of staff recruitment.