The EU treaties are binding agreements between EU Member States. They set out EU objectives, rules for EU institutions, how decisions are made and the relationship between the EU and its Member States. The EU is based on the rule of law, which means that every action taken by the EU is founded on treaties that have been approved voluntarily and democratically by all EU Member States. For example, if a policy area is not cited in a treaty, the European Commission cannot propose a law in that area. Treaties are amended to make the EU more efficient and transparent, to prepare for the accession of new Member States and to introduce new areas of cooperation, such as the single currency (the euro).
Under the treaties, EU institutions can adopt legislation which the Member States then implement. The complete texts of treaties, legislation, case law and legislative proposals can be viewed using the EUR-Lex database of EU law.
The treaties currently in force are:
The main milestones in the development of EU treaties are set out below.
The Treaty establishing the European Coal and Steel Community (ECSC) was signed on 18 April 1951 and entered into force on 23 July 1952; it expired on 23 July 2002. The aim of this Treaty was 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 World War II.
The European Economic Community (EEC) and the European Atomic Energy Community (Euratom) were established in 1957 by the Treaty Establishing the European Economic Community and the Treaty Establishing the European Atomic Energy Community, together known as the Treaties of Rome. The reason for creating the EEC was to create a union of European States that had common economic goals. At that time, many countries were struggling to recover economically from six years of war and this is reflected in the objectives of the original EEC Treaty. These treaties were signed on 25 March 1957 and entered into force on 1 January 1958.
The Merger Treaty (or Brussels Treaty) was signed on 8 April 1965 and entered into force on 1 July 1967. Its aim was to streamline the European institutions by creating a single European Commission and a single European Council to serve the then three European Communities (EEC, Euratom and ECSC). It was later repealed by the Treaty of Amsterdam signed in 1997 and entering into force on 1 May 1999.
By the 1980s, EU Member States had built up their economies once more. The Single European Act (PDF) was signed in February 1986 and entered into force on 1 July 1987. It marked a shift away from dealing with the past (the aftermath of war). Its aim was to create a single market and an area without borders in which the free movement of goods, people, services and capital could take place. It also aimed to reform the EU institutions in light of Portugal's and Spain's impending membership, and to speed up decision-making in preparation for the single market. The main changes introduced by this Treaty were an extension of qualified majority voting in the European Council (making it harder for a single country to veto proposed legislation), and the creation of the cooperation and assent procedures, giving the European Parliament more influence.
The Maastricht Treaty (the Treaty on European Union) was the next important Treaty change. It was signed on 7 February 1992 and entered into force on 1 November 1993, marking the change from the EEC to the EU. This Treaty aimed to prepare the EU for European Monetary Union and introduced elements of a political union – citizenship, and common foreign and internal affairs policy. The main changes introduced by this Treaty were the establishment of the EU and the introduction of the co-decision procedure, which gave Parliament more of a voice in decision-making. New forms of cooperation between EU governments – for example on defence and justice and home affairs – were also introduced. The Maastricht Treaty was seen as an interim measure as it was clear that a number of changes were likely to occur in the very near future, such as the accession of up to 12 new Member States from central and eastern Europe.
The Treaty of Amsterdam (PDF), signed on 2 October 1997 and entering into force on 1 May 1999, aimed to reform the EU institutions in preparation for the arrival of future Member States. It amended and updated the other Treaties and made a number of politically significant changes, particularly in the areas of fundamental rights, employment and the free movement of persons. Its main changes included the amendment, renumbering and consolidation of EU and EEC treaties. It also introduced more transparent decision-making through the increased use of the ordinary legislative procedure.
A month after the Treaty of Amsterdam had come into force, negotiations on the Treaty of Nice had begun. The main purpose of the Treaty of Nice was to prepare for EU enlargement and to deal with matters left over from the Treaty of Amsterdam negotiations, such as changing the structure and decision-making processes in preparation for the expansion of the number of EU Member States to 25. It was considered no longer practical to carry on using the same systems that had been in place since the Treaty of Rome. The Treaty of Nice was signed on 26 February 2001 and entered into force on 1 February 2003. The main changes introduced by this Treaty were changes to the methods for changing the composition of the European Commission and redefining the voting system in the European Council.
The most recent important treaty is the Treaty of Lisbon, signed on 13 December 2007. Its aim was to make the EU more democratic, more efficient and better able to address global problems such as climate change with one voice. The main changes introduced by this treaty were: the introduction of more power for the European Parliament; a change of voting procedures in the European Council; the European Citizens’ Initiative; a permanent president of the European Council; a new High Representative of the Union for Foreign Affairs; and a new EU diplomatic service. Despite being initially rejected by Irish voters in a referendum, the Treaty of Lisbon came into force in 2010 and is the current ruling treaty.
See also: competences of the European Union; Economic and Monetary Union; EU law; opt-out; social competences; Social Policy Protocol; subsidiarity; Treaty establishing a Constitution for Europe; Treaty of Amsterdam; Treaty of Maastricht; Treaty of Nice; Treaty of Paris; Treaty on the Functioning of the European Union; Treaty on Stability, Coordination and Governance; Treaty provisions.
Eurofound (2017), EU Treaties, European Industrial Relations Dictionary, Dublin
https://www.eurofound.europa.eu/en/european-industrial-relations-dictionary/eu-treaties