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.