European Integration: From the Single European Act to the Lisbon Treaty (1986–2009)
The period from the Single European Act (1986) to the Treaty of Lisbon (2007, effective 2009) transformed the European Communities from a primarily economic common market into a political union with extensive competences over matters ranging from monetary policy to justice and home affairs, foreign policy, and fundamental rights. The five treaty revisions of this period — the Single European Act, the Maastricht Treaty, the Treaty of Amsterdam, the Treaty of Nice, and the Treaty of Lisbon — each incrementally expanded the scope of European integration, reformed the institutional structure in response to enlargement and deepening, and addressed the evolving relationship between the Union, its Member States, and their citizens.
The Single European Act (1986)
The Single European Act (SEA), signed in Luxembourg and The Hague on 28 February 1986 and entering into force on 1 July 1987, was the first major revision of the Treaties of Rome. The SEA was a response to the “Eurosclerosis” of the early 1980s — the stagnation of the European integration process, the persistence of non-tariff barriers to trade, and the competitive challenge from the United States and Japan. The SEA’s central objective was the completion of the internal market — defined as “an area without internal frontiers in which the free movement of goods, persons, services and capital is ensured” (Article 8a EEC) — by 31 December 1992.
The most important institutional innovation of the SEA was the introduction of qualified majority voting (QMV) in the Council for measures necessary to achieve the internal market, under the new Article 100a EEC. Previously, Treaty amendments required unanimity for most Council decisions, enabling a single Member State to block legislation. QMV allowed the adoption of internal market measures by a weighted majority of votes (54 out of 76 under the then-10 Member State system), overcoming the national veto that had paralysed harmonisation efforts. The extension of QMV to internal market legislation was the decisive institutional reform that made the 1992 programme feasible.
The SEA formalised European Political Cooperation (EPC) — the intergovernmental coordination of foreign policy among Member States — in Treaty provisions for the first time, establishing a secretariat in Brussels and procedures for consultation and joint action. The Act also established the Court of First Instance (now the General Court) to relieve the caseload burden on the European Court of Justice, particularly in competition and staff cases.
The SEA introduced the cooperation procedure (Article 149(2) EEC), which gave the European Parliament a role in the legislative process for the first time. Under the cooperation procedure, the Parliament could propose amendments to a Council common position, which the Commission could incorporate into its proposal; the Council could then adopt the measure by qualified majority if it accepted the Parliament’s amendments, or by unanimity if it wished to reject them. The cooperation procedure was limited in scope but established the principle that parliamentary participation in legislation was a necessary element of Community decision-making.
The Maastricht Treaty on European Union (1992)
The Treaty on European Union (TEU), signed in Maastricht on 7 February 1992 and entering into force on 1 November 1993, was the most ambitious treaty revision in European integration history. The Maastricht Treaty created the European Union as a new political entity built on three pillars: the European Communities (Pillar I), the Common Foreign and Security Policy (CFSP, Pillar II), and Justice and Home Affairs (JHA, Pillar III). The three-pillar structure reflected different decision-making methods: Pillar I operated according to the supranational Community method (Commission initiative, QMV or unanimity in Council, parliamentary participation, and full judicial review by the Court of Justice); Pillars II and III operated on intergovernmental principles (initiative by Member States or the Commission, unanimity in Council, limited parliamentary consultation, and restricted judicial review).
The Maastricht Treaty introduced European Union citizenship (Article 8 EC), which every national of a Member State automatically acquired as a complement to national citizenship. Union citizenship conferred the right to move and reside freely within the territory of the Member States, the right to vote and stand in municipal and European Parliament elections in the Member State of residence, diplomatic protection by the authorities of any Member State in third countries, and the right to petition the European Parliament and apply to the European Ombudsman. The introduction of Union citizenship was politically symbolic — asserting that the Union was not merely an economic arrangement but a political community — and legally significant, generating litigation on the scope of citizenship rights in cases such as Martinez Sala (1998), Grzelczyk (2001), and Baumbast (2002).
The Treaty established the Economic and Monetary Union (EMU) with a detailed timetable for the introduction of a single currency. EMU proceeded in three stages: Stage I (1990–1993) liberalised capital movements and coordinated economic policies; Stage II (1994–1998) established the European Monetary Institute (the precursor of the European Central Bank) and required Member States to satisfy convergence criteria (price stability, fiscal discipline, exchange rate stability, and convergence of long-term interest rates); Stage III (1999 onwards) irrevocably fixed exchange rates, introduced the euro as the single currency for participating Member States, and transferred monetary policy to the European Central Bank (ECB). The ECB, established in Frankfurt, was given independence from political influence and the primary objective of price stability.
The Maastricht Treaty introduced the co-decision procedure (Article 189b EC), which gave the European Parliament the power to veto legislation by rejecting the Council’s common position in a third reading before a Conciliation Committee. The co-decision procedure transformed the Parliament from a consultative body into a co-legislator with the Council, though initially limited to a small number of policy areas. The Treaty also introduced the principle of subsidiarity (Article 3b EC) — the principle that the Community shall act only “if and in so far as the objectives of the proposed action cannot be sufficiently achieved by the Member States” — as a constitutional constraint on the exercise of Community competences.
The Maastricht Treaty was ratified with difficulty. The Danish electorate rejected the Treaty in a referendum on 2 June 1992 (50.7% against), requiring a second referendum on 18 May 1993 after the Edinburgh Agreement granted Denmark opt-outs from EMU, defence policy, Union citizenship, and JHA cooperation. The French referendum on 20 September 1992 produced a narrow majority in favour (51.05%). The German ratification was delayed by a constitutional challenge before the Federal Constitutional Court, which issued its Maastricht judgment on 12 October 1993, upholding the Treaty but asserting the German Court’s authority to review EU acts for compliance with the principle of democracy and fundamental rights.
The Treaty of Amsterdam (1997)
The Treaty of Amsterdam, signed on 2 October 1997 and entering into force on 1 May 1999, consolidated and extended the Maastricht achievements. The most significant institutional innovation was the communitarisation of asylum, immigration, and visa policy — transferring these matters from the intergovernmental JHA pillar (Pillar III) to the Community pillar (Pillar I), with Commission initiative, QMV in Council, and full ECJ jurisdiction. The Treaty incorporated the Schengen acquis — the 1985 Schengen Agreement and 1990 Schengen Convention on the abolition of internal border controls — into the EU legal framework, with protocols granting opt-outs to the United Kingdom, Ireland, and Denmark.
The Treaty of Amsterdam created the position of the High Representative for the Common Foreign and Security Policy, appointed by the Council to give the EU a visible face in international diplomacy. Javier Solana became the first High Representative in October 1999. The Treaty also established the Policy Planning and Early Warning Unit within the Council Secretariat to support the CFSP.
The Treaty introduced Article 13 EC (now Article 19 TFEU), which empowered the Council to take appropriate action to combat discrimination based on “sex, racial or ethnic origin, religion or belief, disability, age or sexual orientation.” This provision became the legal basis for the far-reaching anti-discrimination directives: Directive 2000/43 on racial equality (the Race Directive), Directive 2000/78 on equal treatment in employment (the Employment Framework Directive), and Directive 2004/113 on gender equality in access to goods and services.
The Amsterdam Treaty strengthened the co-decision procedure, extending it to most of the new policy areas and simplifying the procedure by eliminating the third reading under the cooperation procedure. The Treaty also simplified the legislative procedures by reducing the number of different procedures from over 20 to a more manageable set of basic procedures (consultation, cooperation, co-decision, and assent).
The Treaty of Nice (2001)
The Treaty of Nice, signed on 26 February 2001 and entering into force on 1 February 2003, was designed primarily to prepare the EU’s institutions for the historic enlargement to Central and Eastern Europe. The Treaty reweighted the votes in the Council for a Union of up to 27 Member States: the four largest Member States (Germany, France, Italy, the United Kingdom) received 29 votes each, Spain and Poland received 27, and smaller states received proportionally fewer votes. The Treaty also introduced the “triple majority” requirement: a Council decision under QMV required a majority of Member States (or two-thirds where the proposal did not originate from the Commission), representing at least 62% of the total EU population.
The Treaty of Nice revised the composition of the Commission, providing that from 2005, each Member State would have one Commissioner, but that when the Union reached 27 Member States, the number of Commissioners would be reduced below the number of Member States through a rotation system ensuring “a satisfactory reflection of the demographic and geographical range of the Member States.” (The rotation system was never implemented; the Lisbon Treaty subsequently provided for a Commission composed of one national from each Member State.)
The Nice Treaty extended qualified majority voting to approximately 30 new legal bases, though the French and German governments successfully resisted the extension of QMV to sensitive areas including social security, taxation, and asylum. The Treaty established Eurojust — a unit of prosecutors and magistrates seconded from Member States to coordinate cross-border criminal investigations and prosecutions — as a step toward the creation of a European Public Prosecutor’s Office.
The European Charter of Fundamental Rights was proclaimed by the European Parliament, the Council, and the Commission at the Nice European Council on 7 December 2001. The Charter codified the fundamental rights recognised by the EU legal order: dignity, freedoms, equality, solidarity, citizens’ rights, and justice. The Charter was proclaimed as a political declaration but was not legally binding at Nice; it would become binding primary law only with the entry into force of the Treaty of Lisbon in 2009.
The Failed Constitutional Treaty (2004)
The Laeken Declaration of December 2001 initiated a new phase of constitutional reflection, establishing the European Convention on the Future of Europe, chaired by former French President Valéry Giscard d’Estaing. The Convention, composed of representatives of national governments, national parliaments, the European Parliament, and the Commission, deliberated from February 2002 to July 2003 and produced a Draft Treaty establishing a Constitution for Europe.
The Constitutional Treaty proposed to replace the existing treaties with a single constitutional document, to merge the Union’s separate legal personalities into a single personality, to abolish the three-pillar structure, to strengthen the European Parliament and national parliaments in EU decision-making, to establish a permanent President of the European Council, to create a Union Minister for Foreign Affairs combining the functions of the High Representative and the External Relations Commissioner, to give the Charter of Fundamental Rights binding legal force, and to extend qualified majority voting to new areas.
The Constitutional Treaty was signed in Rome on 29 October 2004 by the 25 Member States. Ratification proceeded in 13 Member States, but the Treaty was rejected by referendums in France (29 May 2005, 54.7% against) and the Netherlands (1 June 2005, 61.5% against). The rejections reflected multiple concerns: economic anxiety, fear of globalisation, opposition to Turkish accession, and a generalised discontent with the political elites. The “period of reflection” declared by the European Council in June 2005 produced no consensus on reviving the Constitutional Treaty, and the constitutional project was abandoned.
The Treaty of Lisbon (2007)
After the failure of the Constitutional Treaty, the EU faced a choice between abandoning institutional reform or salvaging the substance of the Constitutional Treaty in a less politically charged form. The Lisbon Treaty, signed on 13 December 2007 and entering into force on 1 December 2009, adopted the substance of the Constitutional Treaty while abandoning its constitutional symbolism: the term “Constitution” was dropped, the reference to “Union law having primacy over the law of the Member States” was moved to a Declaration, the flag and anthem were not mentioned in the Treaty text, and the symbols of statehood were downplayed.
The Lisbon Treaty abolished the three-pillar structure, creating a single European Union with legal personality (Article 47 TEU). The Treaty on European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU) replaced the existing treaties, with the TEU containing the constitutional provisions and the TFEU containing the detailed sectoral provisions. The Treaty eliminated the distinction between the Community and the Union: the European Community was abolished, and the European Union succeeded it as the sole entity.
The Lisbon Treaty created the office of the permanent President of the European Council, elected by the European Council by qualified majority for a term of two and a half years, renewable once. The President replaced the rotating six-month presidency of the European Council, providing continuity and visibility to the EU’s highest political body. Herman Van Rompuy became the first permanent President in November 2009.
The Treaty established the High Representative of the Union for Foreign Affairs and Security Policy, combining the functions of the former High Representative for CFSP and the Commissioner for External Relations. The High Representative, appointed by the European Council by qualified majority with the agreement of the Commission President, chairs the Foreign Affairs Council and is a Vice-President of the Commission. The Treaty also established the European External Action Service (EEAS) as a diplomatic service supporting the High Representative.
The Lisbon Treaty gave the Charter of Fundamental Rights binding legal force, making it primary law of equivalent status to the Treaties (Article 6(1) TEU). The Protocol on the Application of the Charter to Poland and the United Kingdom (Protocol 30) limited the Charter’s justiciability in those Member States, though its precise legal effect has been the subject of extensive litigation. The Treaty also provided for the EU’s accession to the European Convention on Human Rights (Article 6(2) TEU), though the accession process was delayed by Opinion 2/13 of the Court of Justice of the European Union (18 December 2014), which found the draft accession agreement incompatible with EU law.
The Lisbon Treaty significantly extended the powers of the European Parliament. The co-decision procedure, renamed the ordinary legislative procedure, was extended to over 80 new policy areas, making the Parliament a co-legislator with the Council for the vast majority of EU legislation. The Parliament also acquired the power to elect the President of the Commission on a proposal from the European Council (Article 17(7) TEU), strengthening the politicisation of the Commission presidency and leading to the Spitzenkandidaten process in 2014.
The Treaty introduced the European Citizens’ Initiative (Article 11(4) TEU), enabling one million citizens from at least one-quarter of Member States to request the Commission to submit a legislative proposal on a matter of EU concern. The Treaty extended qualified majority voting to approximately 40 new legal bases, including structural funds, judicial cooperation in criminal matters, and police cooperation, though sensitive areas including taxation, social security, and foreign policy remain subject to unanimity.
The Lisbon Treaty formalised the right of a Member State to withdraw from the Union under Article 50 TEU — a provision that had no equivalent in previous treaties. Article 50 establishes a procedure: the withdrawing state notifies the European Council of its intention, the Union negotiates a withdrawal agreement defining the arrangements for withdrawal and the future relationship, the agreement is adopted by QMV in the Council with the consent of the European Parliament, and the Treaties cease to apply to the withdrawing state on the date of entry into force of the withdrawal agreement or two years after the notification. Article 50 was exercised for the first time by the United Kingdom on 29 March 2017, triggering the Brexit process.
The Treaty of Lisbon thus completed the constitutional transformation of European integration. The period from the Single European Act to Lisbon saw the transition from a common market to a political union, from unanimity to qualified majority voting as the default decision-making rule, from a consultative assembly to a co-legislative Parliament, from a sectoral organisation to a Union with comprehensive competences, and from an international organisation to a constitutional legal order with binding fundamental rights.