Glossary of EU Legal Terms (A-Z)

This glossary defines key legal terms and concepts in European Union law, providing concise explanations for students, practitioners, and anyone seeking to understand the EU legal system.

A

Acquis Communautaire. The entire body of EU law, rights, and obligations binding all Member States. It includes treaties, legislation, case law, international agreements, and general principles. Candidate countries must accept the full acquis before accession.

Advocate General. A member of the European Court of Justice who delivers impartial opinions on cases. Advocates General assist the Court by providing independent legal analysis, though their opinions are not binding on the Court.

Annulment. A legal action under Article 263 TFEU seeking the review of the legality of EU acts. If successful, the Court of Justice declares the act void. Member States, EU institutions, and individuals may bring annulment actions under certain conditions.

C

Charter of Fundamental Rights. The EU’s legally binding human rights instrument, containing 54 articles on dignity, freedoms, equality, solidarity, citizens’ rights, and justice. It became binding under the Treaty of Lisbon in 2009.

Co-decision Procedure. Now the ordinary legislative procedure under Article 294 TFEU, requiring the European Parliament and the Council of the European Union to adopt legislation jointly on an equal footing. It applies to most EU legislative acts.

Comitology. The system of committees composed of Member State representatives that oversee the Commission’s exercise of implementing powers. Committees control how the Commission adopts detailed implementing measures.

Common Foreign and Security Policy (CFSP). The EU’s foreign and security policy framework, governed by intergovernmental decision-making. The High Representative coordinates CFSP, but Member States retain veto power over foreign policy decisions.

Conferral. The principle that the EU acts only within the limits of competences conferred by Member States in the Treaties. Competences not conferred remain with Member States. It is the constitutional foundation of EU authority.

D

Direct Effect. The doctrine enabling individuals to invoke EU law before national courts. Treaty provisions and regulations have full direct effect; directives have vertical direct effect. Established in Van Gend en Loos (1963).

Directive. A legislative act that sets objectives Member States must achieve. Member States choose the form and methods of implementation, transposing directives into national law within specified deadlines.

Double Majority Voting. A voting system in the Council requiring 55% of Member States representing 65% of the EU population. Introduced by the Lisbon Treaty, it replaced the weighted voting system from 2014.

E

Enhanced Cooperation. A mechanism enabling at least nine Member States to adopt legislation within EU frameworks when unanimous agreement is impossible. Used for the European Public Prosecutor’s Office and the Unitary Patent.

EU Citizenship. Citizenship of the Union conferred on every person holding a Member State nationality. Rights include free movement, voting in EU elections, diplomatic protection, and petitioning the European Parliament.

Eurozone. The group of EU Member States that have adopted the euro as their currency. Nineteen Member States currently participate, with others required to join once they meet convergence criteria.

F

Four Freedoms. The fundamental freedoms of the EU single market: free movement of goods, persons, services, and capital. These Treaty rights form the economic foundation of European integration.

Framework Decision. A former legislative instrument under the EU’s third pillar (police and judicial cooperation), replaced by directives under the Lisbon Treaty. Framework decisions could have direct effect and required national transposition.

G

General Principles of EU Law. Unwritten principles developed by the ECJ, including proportionality, legal certainty, legitimate expectations, non-discrimination, and fundamental rights. They bind EU institutions and Member States when implementing EU law.

I

Infringement Procedure. A proceeding under Articles 258-260 TFEU enabling the Commission to take Member States to the Court of Justice for failing to comply with EU law. The Commission may seek financial penalties for non-compliance.

L

Luxembourg Compromise. A 1966 political agreement allowing Member States to veto legislation affecting their vital national interests. It limited majority voting until the Single European Act revived it.

M

Mutual Recognition. A principle derived from Cassis de Dijon requiring Member States to accept goods and services lawfully produced in another Member State, with limited exceptions for public interest objectives.

O

Ordinary Legislative Procedure. The standard EU lawmaking process under Article 294 TFEU, involving equal participation of the European Parliament and the Council. Formerly called the co-decision procedure.

P

Preliminary Reference. A procedure under Article 267 TFEU enabling national courts to refer questions of EU law to the ECJ. It is the primary mechanism for uniform interpretation of EU law across Member States.

Primacy of EU Law. The principle that EU law prevails over conflicting national law, including national constitutions. Established in Costa v ENEL (1964) and recognized in Declaration No. 17 to the Lisbon Treaty.

Proportionality. A general principle requiring that EU measures do not exceed what is necessary to achieve Treaty objectives. It involves a three-part test: suitability, necessity, and proportionality stricto sensu.

Q

Qualified Majority Voting (QMV). A voting system in the Council where decisions require a defined majority of Member States rather than unanimity. Under Lisbon, QMV uses the double majority formula.

R

Regulation. A directly applicable legislative act binding in its entirety and directly effective in all Member States without national transposition. Regulations ensure uniform application of EU law.

S

Single Market. The EU’s integrated economic area without internal frontiers, founded on the four freedoms. It includes harmonized rules, competition policy, and coordinated regulation across 27 Member States.

Subsidiarity. The principle that the EU should act only when objectives cannot be sufficiently achieved by Member States. Article 5(3) TEU codifies subsidiarity, and Protocol No. 2 provides for national parliament oversight.

Supremacy. See Primacy of EU Law.

T

Treaty on European Union (TEU). One of two foundational treaties, containing core constitutional provisions on EU values, objectives, institutions, and external action. Amended substantially by the Lisbon Treaty.

Treaty on the Functioning of the European Union (TFEU). The other foundational treaty, detailing EU competences, policies, and legal instruments. It was formerly the Treaty of Rome.

U

Unanimity. A voting requirement in the Council requiring the consent of all Member States for certain decisions, particularly in CFSP, taxation, and EU accession matters. Unanimity protects national sovereignty in sensitive areas.

V

Vertical Direct Effect. The principle enabling individuals to invoke EU law against the state. Directives have only vertical direct effect; they cannot impose obligations on private parties (Marshall v Southampton, 1986).