Key EU Treaties Every EPSO Candidate Must Know

EU treaty knowledge is a staple of EPSO EU Knowledge tests. You do not need to have read the treaties — but you need to know what each one established, changed, and why it mattered. Here is the essential timeline.

The Foundation: Treaty of Rome (1957)

Official name: Treaty establishing the European Economic Community (EEC)

Key provisions:

• Created the European Economic Community (EEC) — the direct predecessor of the EU
• Established the common market with free movement of goods, services, capital, and persons
• Created the European Commission, Council, Parliament (then called the Assembly), and Court of Justice
• Signed by 6 founding members: Belgium, France, Germany, Italy, Luxembourg, Netherlands

EPSO fact: The Treaty of Rome is also sometimes called the Treaty of the Functioning of the European Union (TFEU) in its current, amended form. Both names may appear in questions.

Single European Act (1986)

Key provisions:

• First major revision of the Treaty of Rome
• Set the deadline for completing the single market by 31 December 1992
• Introduced qualified majority voting in the Council for single market matters (previously unanimity was required for most areas)
• Gave the European Parliament more power through the cooperation procedure

EPSO fact: The Single European Act is often overlooked by candidates, but it was the treaty that enabled the single market as we know it.

Treaty of Maastricht (1992)

Official name: Treaty on European Union (TEU)

Key provisions:

• Created the European Union as a political entity (not just an economic community)
• Established the "three pillars" structure: EC, Common Foreign and Security Policy, Justice and Home Affairs
• Created the path to Economic and Monetary Union (EMU) and the euro
• Introduced EU citizenship
• Strengthened the European Parliament through the co-decision procedure
• Established the Committee of the Regions

EPSO fact: Maastricht is the most frequently tested treaty. Know the three pillars, EMU convergence criteria, and the creation of EU citizenship.

Treaty of Amsterdam (1997)

Key provisions:

• Expanded EU competences in justice, freedom, and security
• Incorporated the Schengen Agreement into EU law
• Strengthened the co-decision procedure (giving Parliament more equal footing with the Council)
• Introduced the position of High Representative for Common Foreign and Security Policy
• Enhanced provisions on fundamental rights and non-discrimination

EPSO fact: Amsterdam is the treaty that brought Schengen into the EU legal framework.

Treaty of Nice (2001)

Key provisions:

• Reformed EU institutions to prepare for the enlargement from 15 to 25+ member states
• Re-weighted votes in the Council
• Reduced the use of unanimity in the Council (more areas moved to qualified majority)
• Capped the number of Commissioners

EPSO fact: Nice was primarily a procedural treaty preparing for enlargement. It is less frequently tested than Maastricht or Lisbon.

Treaty of Lisbon (2007, entered into force 2009)

Key provisions:

• The current constitutional basis of the EU
• Abolished the three pillars (merged into a single framework)
• Created the permanent President of the European Council (previously the role rotated)
• Created the European External Action Service (EEAS) — the EU's diplomatic corps
• Made the Charter of Fundamental Rights legally binding
• Extended the ordinary legislative procedure (co-decision) to most policy areas
• Introduced the citizens' initiative (1 million citizens can invite the Commission to propose legislation)
• Introduced Article 50 — the mechanism for a member state to leave the EU

EPSO fact: Lisbon is the second most tested treaty. Know: permanent European Council President, EEAS, legally binding Charter, Article 50, and citizens' initiative.

Treaty Quick Reference Table

• Rome 1957: EEC, common market, 6 founding members
• Single European Act 1986: Single market completion, QMV expansion
• Maastricht 1992: EU created, three pillars, euro path, EU citizenship
• Amsterdam 1997: Schengen in EU law, High Representative, fundamental rights
• Nice 2001: Institutional reform for enlargement
• Lisbon 2007/2009: Current basis, permanent EC President, EEAS, binding Charter, Article 50

Study Strategy

Focus your memorisation on Maastricht and Lisbon — together they account for the majority of treaty questions. For each treaty, know: the year, the official name, 3-4 key innovations, and one common misconception or trap.