The Treaty of Lisbon (2007)
The Treaty of Lisbon, signed on 13 December 2007, entered into force on 1 December 2009. It amended the Maastricht Treaty and the Treaty of Rome without replacing them, providing the European Union with modernized institutions and enhanced decision-making capacity. Lisbon resolved the institutional impasse following the failure of the Constitutional Treaty and equipped the enlarged EU of 27 Member States to function effectively. It is the most recent major reform of the EU’s constitutional foundations and the legal basis for the current institutional architecture.
Background
The Constitutional Treaty (2004) aimed to consolidate and simplify EU foundational treaties into a single document and was signed by all Member States in Rome. However, it was rejected by French and Dutch voters in referendums in 2005, triggering a constitutional crisis. The Lisbon Treaty retained most of the Constitutional Treaty’s institutional reforms while abandoning constitutional language, symbols (flags, anthems, mottos as legally binding symbols), and the term “constitution.” Negotiations concluded under the German Presidency in 2007, with all Member States ratifying by 2009. Ireland required a second referendum after the initial rejection in 2008, voting in favor in 2009 after obtaining guarantees on tax sovereignty, military neutrality, and ethical issues.
Structural Reforms
Lisbon abandoned the pillar structure established at Maastricht (three pillars: Communities, CFSP, JHA), creating a single legal personality for the EU (Article 47 TEU), enabling the EU to conclude international agreements and join international organizations in its own name. The Treaty on European Union (TEU) retained core constitutional provisions on EU values, objectives, institutions, and common foreign and security policy. The Treaty of Rome was renamed the Treaty on the Functioning of the European Union (TFEU), containing detailed provisions on EU competences, policies, and institutional procedures. The two treaties have equal legal status, with the Charter of Fundamental Rights (proclaimed in 2000) acquiring binding legal force.
The Lisbon Treaty also introduced provisions on democratic principles for the first time. Article 10 TEU establishes representative democracy as the foundation of EU governance, with citizens directly represented in the European Parliament and Member States represented in the Council. Article 11 TEU introduces participatory democracy, including the European Citizens’ Initiative (ECI), which allows one million citizens from a significant number of Member States to invite the Commission to propose legislation.
Institutional Changes
The Treaty created the permanent President of the European Council, elected by the European Council by qualified majority for a two-and-a-half-year term (renewable once). The first holder was Herman Van Rompuy. The President chairs European Council meetings, ensures preparation and continuity, and represents the EU externally on CFSP matters at his or her level. The High Representative of the Union for Foreign Affairs and Security Policy merged the roles of External Relations Commissioner and CFSP High Representative, becoming a Vice-President of the Commission and chairing the Foreign Affairs Council.
The European Parliament’s legislative and budgetary powers were significantly expanded. Co-decision (renamed the ordinary legislative procedure) was extended to over 40 new policy areas, making the Parliament a co-legislator on equal footing with the Council across most EU legislation. The Parliament also gained increased powers over the EU budget and international agreements. The number of MEPs was capped at 750 plus the President. The Commission was restructured: from 2014, the number of Commissioners would correspond to two-thirds of Member States (this was later reversed by the European Council in 2009, maintaining one Commissioner per Member State).
Voting and Decision-Making
The Treaty introduced double majority voting in the Council (Article 16(4) TEU), requiring 55% of Member States representing at least 65% of the EU population for qualified majority voting. This replaced the complex weighting system established by the Nice Treaty. The new system was phased in from 1 November 2014 to 31 March 2017, during which a Member State could request application of the old Nice weights. The transitional period allowed Member States to adapt to the new system.
National parliaments received subsidiarity monitoring powers through the early warning mechanism under Protocol No. 2. Any national parliament may issue a reasoned opinion within eight (now twelve) weeks if it believes a legislative proposal violates subsidiarity. If one-third of national parliaments object (one-quarter for justice and home affairs), the Commission must review the proposal (yellow card). If a majority of national parliaments objects under the ordinary legislative procedure, the Council or Parliament may block the proposal (orange card).
Enhanced Cooperation
Lisbon simplified provisions for enhanced cooperation (Articles 326–334 TFEU), enabling groups of at least nine Member States to pursue deeper integration in specific areas using EU institutions and procedures. The mechanism requires that enhanced cooperation not undermine the single market or discriminate between Member States. It has been used for the European Public Prosecutor’s Office (EPPO), the Unitary Patent, the Property Regime for International Couples, and the Financial Transaction Tax (authorized but not yet implemented). Enhanced cooperation accommodates diversity within the single institutional framework, allowing integration to proceed at variable speeds without requiring all Member States to participate.
Fundamental Rights
The Charter of Fundamental Rights became legally binding under Article 6(1) TEU, with the same legal value as the Treaties. The EU committed to accede to the European Convention on Human Rights under Article 6(2) TEU, though accession has not been completed due to the incompatibilities identified in Opinion 2/13 of the ECJ (2014). Article 6(3) TEU confirms that fundamental rights, as guaranteed by the ECHR and as they result from the constitutional traditions common to Member States, constitute general principles of EU law, maintaining the pre-existing protection alongside the Charter.
Foreign Policy
The Treaty established the European External Action Service (EEAS) to support the High Representative and coordinate EU diplomatic representation. The EEAS comprises officials from the Commission, the Council Secretariat, and national diplomatic services, serving as the EU’s diplomatic corps. The Treaty extended EU competence in foreign affairs, humanitarian aid, and development cooperation while maintaining intergovernmental decision-making in CFSP, where unanimity remains the rule with limited use of constructive abstention.
Exit Clause
Article 50 TEU introduced a withdrawal mechanism allowing any Member State to leave the EU. The provision was drafted without expectation of use until the United Kingdom invoked it on 29 March 2017, following the June 2016 referendum. Article 50 proved workable but incomplete: the two-year negotiation period could be extended by unanimous agreement, but the status of the withdrawing state during negotiations remained contested, particularly regarding participation in EU decision-making. The UK’s departure demonstrated procedural gaps that subsequent practice filled, including the separation agreement (Withdrawal Agreement), the framework for future relations (Political Declaration), and the treatment of citizens’ rights, financial settlement, and Irish border issues.
EU Competences
The Lisbon Treaty introduced a systematic classification of EU competences for the first time. Article 2–6 TFEU distinguish exclusive competences (customs union, competition, monetary policy for euro area, common commercial policy, certain fisheries), shared competences (internal market, environment, consumer protection, transport, energy, area of freedom, security and justice, certain public health matters), and supporting competences (education, culture, tourism, administrative cooperation). The principle of conferral (Article 5 TEU) limits EU action to competences conferred by Member States. The flexibility clause (Article 352 TFEU) allows EU action necessary to attain Treaty objectives where the Treaties have not provided the necessary powers, subject to unanimity and Parliament consent.