Treaties

There are four basic types of legal documents on which the European Union and the European Communities are founded:

1. Founding Treaties
2. Amending Treaties
3. Accession Treaties for each of the five enlargements
4. Other essential documents such as the Constitution

Founding Treaties

European integration is based on four founding treaties:

• The European Coal and Steel Community (1951)
  The Treaty establishing the European Coal and Steel Community (ECSC), which was signed on 18 April 1951 in Paris, entered into force on 23 July 1952 and expired on 23 July 2002;
• The European Economic Community (1957)
  The Treaty establishing the European Economic Community (EEC);
• The European Atomic Energy Community (1957)
  The Treaty establishing the European Atomic Energy Community (Euratom), which was signed (along with the EEC Treaty) in Rome on 25 March 1957, and entered into force on 1 January 1958. These 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 European Union (1992)
  The Treaty on European Union, which was signed in Maastricht on 7 February 1992, entered into force on 1 November 1993. 'The Maastricht Treaty changed the name of the European Economic Community to simply "the European Community". It also introduced new forms of co-operation between the Member State governments - for example on defence, and in the area of "justice and home affairs". By adding this inter-governmental co-operation to the existing "Community" system, the Maastricht Treaty created a new structure with three "pillars" which is political as well economic. This is the European Union (EU).

Amending Treaties

The founding treaties have been amended on several occasions, in particular when new Member States acceded in 1973 (Denmark, Ireland, United Kingdom), 1981 (Greece), 1986 (Spain, Portugal) and 1995 (Austria, Finland, Sweden). There have also been more 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 (SEA), 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: it amended and renumbered the EU and EC Treaties. Consolidated versions of the EU and EC Treaties are attached to it. The Treaty of Amsterdam changed the articles of the Treaty on European Union, identified by letters A to S, into numerical form;
• The Treaty of Nice, signed on 26 February 2001, entered into force on 1 February 2003. The Treaty of Nice, the former Treaty of the EU and the Treaty of the EC have been merged into one consolidated version.

Further changes will probably be made to the Treaties as a result of the Convention on the Future of Europe and of the Treaty on the Accession of 10 new Member States, which was signed on 16 April 2003 and came into force on 1 May 2004.

Accession Treaties

The founding treaties have also been amended (in a more limited fashion) whenever new member states acceded:

• Treaty of Accession 2005 signed in Luxembourg on 13 April 2005 (Bulgaria, Romania) (2005) 
• Accession of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia (2003)
• Appendices to Annexes IV, V, VII, VIII, IX, X, XI, XII, XIII and XIV of the Act concerning the conditions of accession of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia
• Accession of Austria, Finland and Sweden (1994)
• Accession of Austria, Finland and Sweden (Adaptation decision 1995)
• Accession of Spain and Portugal, signed in Madrid and Lisbon on 12 June (1986)
• Accession of Spain and Portugal (1985)
• Accession of Greece (1979)
• Accession of Denmark, Ireland and the United Kingdom (Adaptation decision 1973)
• Accession of Denmark, Ireland and the United Kingdom (1972)

Other Treaties and Protocols

• Amending Treaties
• Single European Act (1986)
• Greenland Treaty (1984)
• Protocol on the Statute of the European Investment Bank (1975)
• Treaty amending certain financial provisions (1975)
• Treaty amending certain budgetary provisions (1970)
• Merger Treaty (1965)
• Protocol on the Netherlands Antilles (1962) 

European Constitution

The European Constitution aims to consolidate, simplify and replace the existing set of overlapping treaties. It was signed on 29 October 2004 and entered into force on 1 November 2006. During the process of ratification, The French (on 29 May 2005) and then the Dutch (on 1 June 2005) rejected the treaty in referenda. This might spell the end of the constitution. If the Constitution fails to be ratified by all member states, the EU will continue to work on the basis of the current treaties as described above.