The treaties of the European Union are effectively its constitutional law, making up the EU's primary legislation.

Current treaties

Founding treaties

European integration is at present based on four founding treaties:

• The Treaty of Paris, establishing the European Coal and Steel Community, which was signed on 18 April 1951, entered into force on 23 July 1952 and expired on 23 July 2002.
• The Treaty establishing the European Atomic Energy Community (Euratom)
• The Treaty establishing the European Economic Community (EEC), which was signed - along with the Euratom Treaty - in Rome on 25 March 1957, and entered into force on 1 January 1958. These two Treaties are often referred to as the "Treaties of Rome". When the term "Treaty of Rome" is used, only the EEC Treaty is meant.
• The Treaty on European Union, signed in Maastricht on 7 February 1992, entered into force on 1 November 1993. It changed the name of the European Economic Community to simply "the European Community" and introduced new intergovermental structures to deal with the aspects of Common Foreign and Security Policy and "Justice and Home Affairs". The structure formed by these so-called Three Pillars is the European Union, whose scope was now more overtly political as well as economic.

Amending treaties

At times there have been far-reaching reforms bringing major institutional changes and introducing new areas of responsibility for the European institutions:

• The Merger Treaty, signed in Brussels on 8 April 1965 and in force since 1 July 1967, provided for a Single Commission and a Single Council of the then three European Communities.
• The Single European Act, signed in Luxembourg and The Hague, and entered into force on 1 July 1987, provided for the adaptations required for the achievement of the Internal Market.
• The Treaty of Amsterdam, signed on 2 October 1997, entered into force on 1 May 1999.
  • Its purpose was to simplify decision making in addition to further integrating the Common Foreign and Security Policy concept. It also added new provisions on social policy and employment and integrated the Schengen Agreement.
  • It amended and renumbered the EU and EC Treaties. The articles of the Treaty on European Union (the Maastricht Treaty), identified in that document by letters A to S, were changed into numerical form. Consolidated versions of the EU and EC Treaties are attached to it.
• The Treaty of Nice, signed on 26 February 2001, entered into force on 1 February 2003.
  • It readied the EU for further enlargement, setting a cap on the number of MEPs (732) and the European Commission (25). The latter point meant that larger countries would go from two commissioners to one.
  • Qualified Majority Voting was again extended to more areas, abolishing the national right to veto in some areas. A concept of "enhanced co-operation" was introduced for countries wishing to forge closer links in areas where other states disagreed.

Treaties of Accession

Main article: Enlargement of the European Union

The founding treaties have also been amended (in a more limited fashion) whenever new Member States acceded.

• 1973: Acts of Accession of Denmark, Ireland, Norway and the United Kingdom, signed in Brussels on 22 January 1972. (Norway failed to ratify and did not join the EU.)
• 1981: Act of Accession of Greece, signed in Athens on 28 May 1979.
• 1986: Acts of Accession of Spain and Portugal, signed in Madrid and Lisbon on 12 June 1985.
• 1995: Acts of Accession of Austria, Sweden, Finland and Norway, signed at the Corfu European Council on 24 June 1994. (Norway again failed to ratify.)
• 2004: Treaty of Accession 2003 signed in Athens on 16 April 2003 (Cyprus, Czech Republic, Estonia, Hungary, Lithuania, Latvia, Malta, Poland, Slovenia, Slovakia).

Budgetary treaties

Lastly there have been two budgetary treaties:

• The Budgetary Treaty of 1970 (more fully the "Treaty amending Certain Budgetary Provisions of the Treaties establishing the European Communities and of the Treaty establishing a Single Council and a Single Commission of the European Communities"), signed in Luxembourg on 22 April 1970, gave the European Parliament the last word on what is known as "non-compulsory expenditure". It came into force on 1 January 1971.

• The Budgetary Treaty of 1975 (more fully the "Treaty amending Certain Financial Provisions of the Treaty establishing the European Communities and of the Treaty establishing a Single Council and a Single Commission of the European Communities") , signed in Brussels on 22 July 1975, gave the European Parliament the power to reject the budget as a whole, and created the European Court of Auditors. It came into force on 1 June 1977.

European Constitution

Main article: Treaty establishing a constitution for Europe

On 18 June 2004, all 25 member states represented by their Prime Ministers or Presidents in the European Council approved a draft European Constitutional Treaty, which was signed by them on 29 October 2004.

This European Constitution as it is informally known will consolidate, simplify and replace all existing treaties underlying the European Union after it has been approved by all 25 member states. As many of those are planning referendums, this approval process is likely to be fraught with difficulty and it will take a couple of years at the very least.

In the meanwhile, or if the European Constitution does not have enough momentum to gain approval in all member states, the EU will continue to work on the basis of the current treaties described above.

Acknowledgement

Based on text from the EU website (http://europa.eu.int/abc/treaties_en.htm) which states "© European Communities, 1995-2004 Reproduction is authorised, provided the source is acknowledged, save where otherwise stated. Where prior permission must be obtained for the reproduction or use of textual and multimedia information (sound, images, software, etc.), such permission shall cancel the above-mentioned general permission and shall clearly indicate any restrictions on use.