The Treaty of Lisbon

The picture shows the logo of the Lisbon Treaty. This was signed by the EU member states in 2007 and ratified in 2009.
Closer to the citizens and more transparency: The Lisbon Reform Treaty has not replaced but updated previous treaties. © European Union

After the treaty intended to create a consolidated constitution for the European Union was not ratified, the existing EU treaties were amended and expanded. The institutional changes provided for in the original treaty were, however, carried over. This resulted in the Treaty of Lisbon, which also regulates the withdrawal of member states. The United Kingdom chose to withdraw from the EU on 31 January 2020.

In October 2004 the European Council signed the Treaty establishing a Constitution for Europe, the goal of which was to create a constitution for Europe to replace the multitude of existing treaties and more clearly restructure the legal foundation of the EU. The aim was to make the EU more efficient in decision-making, more transparent, more democratic, and closer to citizens. But in May and June 2005 the Constitutional Treaty was rejected in popular referendums in France and the Netherlands.

Towards the new Reform Treaty

In June 2007 the heads of state and governments of the EU member states agreed in principle to replace the original Constitutional Treaty with a new EU Reform Treaty. The most important institutional innovations of the Constitutional Treaty were maintained so that the decision-making ability, efficiency, and proximity to the citizenry would be adequately guaranteed in a growing EU. On 13 December 2007, the EU member states signed the new treaty in Portugal, which became known as the Treaty of Lisbon. The treaty was to be ratified by all member states by 2009.

However, in the first vote on the treaty, in June 2008, Irish voters rejected it. Following concessions made by the European Council to Ireland, the Irish government called a new vote on 2 October 2009, in which the treaty was endorsed. After ratification of the treaty by Poland and lastly the Czech Republic, it came into force on 1 December 2009.

Reform of existing treaties instead of a constitution

The Treaty of Lisbon did not replace earlier treaties. Instead, it amended the treaties that form the constitutional basis of the EU, which were newly renamed the Treaty on European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU). The Treaty of Lisbon retained the most important aspects of the Constitutional Treaty. It reformed the EU's political system and abolished the existing three-pillar model, for example. Internal coordination mechanisms were developed, the veto powers of individual member states was curtailed, and additional powers were handed over to Parliament. The EU also acquired legal personality, so it can act as an independent institution in terms of its Common Foreign and Security Policy.


In 2009, the TEU introduced the possibility for member states to withdraw from the EU – contained in Article 50 of the Treaty.  On 23 June 2016, the majority of the United Kingdom electorate voted to leave the EU.  This decision was finalised on 31 January 2020. During the transition phase, the UK remained in the single European market until the end of 2020.