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🇪🇺European History – 1945 to Present

Major European Union Treaties

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Why This Matters

The European Union didn't emerge fully formed—it was built treaty by treaty, each agreement responding to specific historical pressures and expanding the scope of integration. You're being tested on your ability to trace this evolution: how postwar fears of conflict drove early economic cooperation, how economic success created momentum for political union, and how each treaty balanced national sovereignty against supranational authority. Understanding this trajectory is essential for answering questions about European identity, the tensions between integration and nationalism, and the EU's role in the post-Cold War order.

Don't just memorize treaty names and dates—know what problem each treaty solved and what new powers it created. The AP exam loves asking about turning points and causation, so focus on why leaders chose deeper integration at specific moments and what mechanisms (qualified majority voting, common citizenship, shared currency) actually made the EU function. When you can explain how the Treaty of Paris's narrow focus on coal and steel evolved into Maastricht's European citizenship, you've mastered the conceptual arc.


Postwar Foundations: Preventing Conflict Through Economic Integration

The earliest treaties emerged from a simple but revolutionary idea: nations that trade together don't fight each other. By binding France and Germany's war-making industries together, European leaders sought to make another continental war materially impossible.

Treaty of Paris (1951)

  • Created the European Coal and Steel Community (ECSC)—the first supranational organization in Europe, pooling control of industries essential for warfare
  • Six founding members (France, West Germany, Italy, Belgium, Netherlands, Luxembourg) surrendered national control over coal and steel production to a shared High Authority
  • Established the "Schuman Plan" model—proving that former enemies could integrate economically, creating the template for all future European cooperation

Treaties of Rome (1957)

  • Established the European Economic Community (EEC) and EURATOM—expanding integration beyond coal and steel to create a comprehensive common market
  • Four freedoms became the foundation: free movement of goods, services, capital, and labor across member borders
  • Shifted integration from war prevention to prosperity—the EEC's success in boosting trade created political momentum for deeper cooperation

Compare: Treaty of Paris vs. Treaties of Rome—both pursued integration through economics, but Paris targeted specific war industries while Rome created a broad common market. If an FRQ asks about the evolution of European integration, use this shift from security-focused to prosperity-focused cooperation.


Institutional Consolidation: Building a Functional Bureaucracy

As European cooperation expanded, the patchwork of institutions became unwieldy. These treaties streamlined governance and prepared the Communities for more ambitious integration.

Merger Treaty (1965)

  • Unified three separate executives into a single European Commission and Council of Ministers—ending the inefficiency of parallel bureaucracies for ECSC, EEC, and EURATOM
  • Created the institutional architecture that would eventually become the EU's governing structure
  • Demonstrated commitment to "ever closer union"—member states chose efficiency over maintaining separate national influence in each community

Single European Act (1986)

  • Set the 1992 deadline for completing the internal market—eliminating remaining barriers to trade, from customs delays to incompatible product standards
  • Introduced qualified majority voting (QMV) in the Council, allowing decisions without unanimous consent and preventing single-country vetoes on market issues
  • Expanded scope beyond economics—added environmental policy, social policy, and regional development to European competence for the first time

Compare: Merger Treaty vs. Single European Act—both strengthened institutions, but the Merger Treaty consolidated existing structures while the SEA fundamentally changed how decisions were made (QMV) and what the EC could regulate. The SEA marks the shift toward political integration.


The Maastricht Moment: From Community to Union

The end of the Cold War created both opportunity and pressure for deeper integration. The Maastricht Treaty represented the most ambitious leap yet—transforming an economic community into a political union with shared citizenship and a common currency.

Maastricht Treaty (1992)

  • Created the European Union and established the path to Economic and Monetary Union (EMU)—committing members to adopt a single currency (the euro) by decade's end
  • Introduced European citizenship—for the first time, individuals held rights as EU citizens, including the right to live, work, and vote in local elections anywhere in the Union
  • Established the "three pillars": the European Communities (economics), Common Foreign and Security Policy, and Justice and Home Affairs—expanding cooperation into traditionally sovereign domains

Compare: Treaties of Rome vs. Maastricht Treaty—Rome created economic integration among nations; Maastricht created political union with shared citizenship. This is the pivotal transformation from the EEC to the EU. Know this distinction cold for any question about European identity or sovereignty.


Enlargement and Reform: Preparing for a Bigger Union

With the Cold War over and Eastern European nations eager to join, the EU faced a structural problem: institutions designed for six members couldn't function with twenty-five. These treaties reformed voting systems and clarified powers to accommodate expansion.

Amsterdam Treaty (1997)

  • Strengthened the European Parliament's powers—increasing democratic accountability as the EU took on more authority over citizens' lives
  • Incorporated the Schengen Agreement into EU law—making border-free travel a formal EU policy rather than a separate arrangement
  • Enhanced cooperation on justice and immigration—moving these sensitive areas closer to supranational governance while allowing some opt-outs

Nice Treaty (2001)

  • Reformed voting weights in the Council to prepare for Eastern enlargement—rebalancing power between large and small states
  • Expanded qualified majority voting to more policy areas—reducing veto points that could paralyze an enlarged Union
  • Acknowledged institutional limits—the treaty's complexity revealed the need for more fundamental reform, leading to the failed Constitutional Treaty

Compare: Amsterdam vs. Nice—both prepared for enlargement, but Amsterdam focused on policy scope (Schengen, justice cooperation) while Nice tackled the mechanical problem of voting weights. Together they show the EU struggling to maintain effectiveness while growing.


Constitutional Ambitions and Pragmatic Solutions

After voters in France and the Netherlands rejected a formal EU Constitution in 2005, leaders salvaged most reforms in treaty form—avoiding the symbolic weight of "constitution" while achieving similar institutional changes.

Lisbon Treaty (2007)

  • Created permanent EU leadership positions—a President of the European Council (2.5-year terms) and High Representative for Foreign Affairs gave the EU recognizable faces on the world stage
  • Made the Charter of Fundamental Rights legally binding—enshrining civil, political, economic, and social rights as enforceable EU law
  • Further empowered the European Parliament—expanding co-decision (now "ordinary legislative procedure") to make Parliament a true co-legislator with the Council in most areas

Compare: Maastricht vs. Lisbon—Maastricht created the EU's basic structure; Lisbon refined it for the 21st century. Both expanded Parliament's power and deepened political integration, but Lisbon responded specifically to criticisms about the EU's democratic deficit and lack of coherent foreign policy voice.


Quick Reference Table

ConceptBest Examples
Preventing conflict through economic integrationTreaty of Paris, Treaties of Rome
Institutional consolidationMerger Treaty, Single European Act
Qualified majority voting (ending unanimity)Single European Act, Nice Treaty
Creating political union / European citizenshipMaastricht Treaty
Economic and Monetary Union (euro)Maastricht Treaty
Preparing for enlargementAmsterdam Treaty, Nice Treaty
Democratic legitimacy / Parliament's powerAmsterdam Treaty, Lisbon Treaty
Supranational leadership positionsLisbon Treaty

Self-Check Questions

  1. Which two treaties most directly addressed the challenge of maintaining EU effectiveness while adding new member states, and what specific reforms did each introduce?

  2. How did the Single European Act change EU decision-making, and why was this shift necessary for completing the internal market?

  3. Compare the Treaty of Paris and the Maastricht Treaty: what did each establish, and how do they represent different stages in the evolution from economic cooperation to political union?

  4. If an FRQ asked you to explain the EU's "democratic deficit," which treaties would you cite as attempts to address this problem, and what mechanisms did they create?

  5. Why did the Maastricht Treaty represent a more significant transformation than the Treaties of Rome, even though Rome created the common market?