How did the Lisbon Treaty change the European Union’s institutions?

The Lisbon Treaty, which entered into force on December 1, 2009, introduced significant reforms to streamline and strengthen the European Union’s institutional framework:

• Executive and Leadership Roles: The treaty created the permanent office of the president of the European Council to provide a consistent face for the EU. It also established the position of high representative for foreign affairs and security policy to unify the EU’s foreign policy representation.1
• Legislative and Decision-Making Power: The European Parliament saw its legislative powers expanded, particularly through the extension of the codecision procedure to many new policy areas. Within the Council of the European Union, the treaty introduced a "double majority" voting rule—requiring 55 percent of member states representing 65 percent of the EU population—to simplify and accelerate decision-making.21
• Institutional Structure: The European Community was formally incorporated into the EU, and the Charter of Fundamental Rights became legally binding. Additionally, the treaty introduced the European Citizens’ Initiative, allowing citizens to directly petition the European Commission.1
• Commission Composition: Provisions were made to eventually reduce the number of commissioners to two-thirds of the number of member states, moving toward a rotating system.3