Founding agreements

European Union (EU), international organization comprising 27 European countries and governing common economic, social, and security policies. Originally confined to western Europe, the EU undertook a robust expansion into central and eastern Europe in the early 21st century. The EU’s members are Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, and Sweden. The United Kingdom, which had been a founding member of the EU, left the organization in 2020.

The EU is based on the rule of law. This means that every action taken by the EU is founded on treaties that have been approved voluntarily and democratically by all EU member countries. For example, if a policy area is not cited in a treaty, the Commission cannot propose a law in that area.

A treaty is a binding agreement between EU member countries. It sets out EU objectives, rules for EU institutions, how decisions are made and the relationship between the EU and its member countries.

Treaties are amended to make the EU more efficient and transparent, to prepare for new member countries and to introduce new areas of cooperation – such as the single currency.

Under the treaties, EU institutions can adopt legislation, which the member countries then implement. The complete texts of treaties, legislation, case law and legislative proposals can be viewed using the EUR-Lex database of EU law.

Treaty of Lisbon

Signed: 13 December 2007
Entered into force: 1 December 2009

Purpose: to make the EU more democratic, more efficient and better able to address global problems, such as climate change, with one voice.

Main changes: more power for the European Parliament, change of voting procedures in the Council, citizens’ initiative, a permanent president of the European Council, a new High Representative for Foreign Affairs, a new EU diplomatic service.

The Lisbon treaty clarifies which powers:
– belong to the EU
– belong to EU member countries
– are shared.

The goals and values of the EU and are laid out in the Lisbon Treaty and the EU Charter of fundamental rights. Full text of the Treaty of Lisbon

Treaty of Nice

Signed: 26 February 2001
Entered into force: 1 February 2003

Purpose: to reform the institutions so that the EU could function efficiently after reaching 25 member countries.

Main changes: methods for changing the composition of the Commission and redefining the voting system in the Council.

Full text of the Treaty of Nice

Treaty of Amsterdam

Signed: 2 October 1997
Entered into force: 1 May 1999

Purpose: To reform the EU institutions in preparation for the arrival of future member countries.

Main changes: amendment, renumbering and consolidation of EU and EEC treaties. More transparent decision-making (increased use of the ordinary legislative procedure).

Full text of the Treaty of Amsterdam

Treaty on European Union - Maastricht Treaty

Signed: 7 February 1992
Entered into force: 1 November 1993

Purpose: to prepare for European Monetary Union and introduce elements of a political union (citizenship, common foreign and internal affairs policy).

Main changes: establishment of the European Union and introduction of the co-decision procedure, giving Parliament more say in decision-making. New forms of cooperation between EU governments – for example on defence and justice and home affairs.

Full text of the Maastricht Treaty

Single European Act

Signed: 17 February 1986 (Luxembourg) / 28 February 1986 (The Hague)

Entered into force: 1 July 1987

Purpose: to reform the institutions in preparation for Portugal and Spain’s membership and speed up decision-making in preparation for the single market.

Main changes: extension of qualified majority voting in the Council (making it harder for a single country to veto proposed legislation), creation of the cooperation and assent procedures, giving Parliament more influence.

Full text of the Single European Act

Merger Treaty - Brussels Treaty

Signed: 8 April 1965
Entered into force: 1 July 1967

Purpose: to streamline the European institutions.

Main changes: creation of a single Commission and a single Council to serve the then three European Communities (EEC, Euratom, ECSC). Repealed by the Treaty of Amsterdam.

Full text of the Merger Treaty

Treaty of Rome: EEC and EURATOM treaties

Signed: 25 March 1957
Entered into force: 1 January 1958

Purpose: to set up the European Economic Community (EEC) and the European Atomic Energy Community (Euratom).

Main changes: extension of European integration to include general economic cooperation.

Full text of the Treaty establishing the European Economic Community
Full text of the Treaty establishing the European Atomic Energy Community

Treaty establishing the European Coal and Steel Community

Signed: 18 April 1951

Entered into force: 23 July 1952

Expired: 23 July 2002

Purpose: to create interdependence in coal and steel so that one country could no longer mobilise its armed forces without others knowing. This eased distrust and tensions after WWII. The ECSC treaty expired in 2002.

Full text of the Treaty establishing the European Coal and Steel Community