The EU's member states gathered to sign the Treaty of Lisbon, a pivotal document that would revamp the constitutional foundation of the European Union. By amending the Treaty of Rome and the Maastricht Treaty, this new treaty sought to streamline the EU's institutions, enhance its decision-making processes, and strengthen its global role. Effective from December 1, 2009, the Treaty of Lisbon aimed to create a more united, efficient, and influential European Union, ultimately benefiting its citizens and the world at large.