Which treaties built the European Union, from Rome to Lisbon?

The European Union was built by a stack of treaties rather than by one founding document. Three landmarks are the Treaty of Rome (signed 1957), the Maastricht Treaty (1992) and the Treaty of Lisbon (2007). Today the EU rests on two main treaties: the Treaty on European Union, which comes from Maastricht, and the Treaty on the Functioning of the European Union, which is the Treaty of Rome in updated form.

Rome came first. Six countries, Belgium, France, Italy, Luxembourg, the Netherlands and West Germany, signed it on 25 March 1957, and it came into force on 1 January 1958. It proposed to cut customs duties step by step, set up a customs union and create a common market for goods, labour, services and capital.

Maastricht, concluded in 1992, announced "a new stage in the process of European integration": a shared European citizenship, the eventual introduction of a single currency and, with less precision, common foreign and security policies. The European Union as such was established when it came into force in 1993. Many saw it as a step toward a "federal Europe", yet key areas stayed intergovernmental, with national governments deciding together.

Lisbon, signed on 13 December 2007 and in force since 1 December 2009, amended both earlier treaties. It made the Charter of Fundamental Rights legally binding and, for the first time, gave member states an explicit legal right to leave.

The treaties matter for one more reason: the EU can only act within the powers they give it, and changing them needs every signatory to agree and ratify under its own national procedures. That helps explain why treaty change is slow.