Sources and Hierarchy of EU Law
The sources of European Union law form a structured hierarchy reflecting the constitutional character of the EU legal order. At the apex stand the Treaties and the Charter of Fundamental Rights as primary law, followed by general principles of EU law developed by the Court of Justice, international agreements binding on the Union, and secondary legislation adopted by the EU institutions. Within secondary law, a further hierarchy distinguishes basic legislative acts from delegated and implementing acts. This normative structure ensures legal certainty, uniformity, and the rule of law across the Union while accommodating the diversity of legal instruments through which EU law operates.
Primary Law
Primary law constitutes the highest source of EU law, possessing constitutional status. It comprises the Treaty on European Union (TEU), the Treaty on the Functioning of the European Union (TFEU), and the Charter of Fundamental Rights, which Article 6(1) TEU accords the same legal value as the Treaties. The Protocols annexed to the Treaties and the accession treaties of new Member States also form part of primary law under Article 51 TEU.
The Treaties function as the constitutional charter of the European Union. The CJEU has described them as a “constitutional charter” in Opinion 1/91 (on the EEA Agreement), reflecting their character as the foundational source of EU law that establishes the Union’s objectives, institutions, competences, and procedures. Primary law prevails over all other sources of EU law and determines the validity of secondary legislation. Any EU act that conflicts with the Treaties or the Charter is voidable before the CJEU.
Amendments to primary law require the special procedures set out in Article 48 TEU, involving a Convention, an Intergovernmental Conference, and ratification by all Member States in accordance with their constitutional requirements. This rigorous amendment procedure underscores the constitutional character of the Treaties and distinguishes them from ordinary legislation.
General Principles of EU Law
General principles of EU law are unwritten sources of law developed by the CJEU to fill gaps in the written law and to ensure coherence and fundamental justice within the EU legal order. They rank below the Treaties but above secondary legislation and serve as grounds for reviewing the validity of EU acts and Member State measures implementing EU law.
The CJEU has recognised a wide range of general principles. Proportionality, derived from German constitutional law, requires that EU measures be appropriate and necessary to achieve legitimate objectives and not impose excessive burdens on individuals (Fedesa, Case C-331/88). Subsidiarity, codified in Article 5(3) TEU, provides that the Union shall act only where the objectives of proposed action cannot be sufficiently achieved by Member States. Legal certainty requires that EU law be clear, predictable, and not retroactive unless exceptionally justified (Racke, Case 98/78). Legitimate expectations protects individuals who have relied on EU measures or assurances (Mulder, Cases C-104/89 and C-37/90). Non-discrimination on grounds of nationality (Article 18 TFEU) and on other grounds is a foundational principle. Equal treatment requires that comparable situations not be treated differently unless objectively justified. Effectiveness requires that national procedural rules not render the exercise of EU rights practically impossible or excessively difficult. Sincere cooperation under Article 4(3) TEU imposes duties of mutual assistance and loyalty between the Union and Member States.
Fundamental rights, as recognised in the Charter and as general principles of EU law, constitute a further category of general principles. The CJEU in Internationale Handelsgesellschaft (Case 11/70) held that fundamental rights form an integral part of the general principles of EU law, drawing inspiration from national constitutional traditions and the ECHR. Even after the Charter became binding, general principles continue to provide an independent source of fundamental rights protection, particularly where the Charter’s scope may be limited.
International Agreements
International agreements concluded by the Union under Article 216(2) TFEU are binding on the EU institutions and Member States. They rank below primary law but above secondary legislation. The CJEU in Intertanko (Case C-308/06) held that the validity of EU secondary legislation may be reviewed against international agreements where the nature and broad logic of the agreement do not preclude such review and the agreement’s provisions are unconditional and sufficiently precise.
The rank of international agreements in the EU legal hierarchy depends on their subject matter and the context in which they are invoked. Mixed agreements, concluded by both the Union and Member States, give rise to complex questions of competence and interpretation. The CJEU has exclusive jurisdiction to interpret agreements concluded by the Union and to determine the division of competence between the Union and Member States in relation to mixed agreements.
The Union’s international agreements include trade agreements, association agreements, cooperation agreements, and sectoral agreements in areas including environment, transport, and research. The Common Commercial Policy under Article 207 TFEU is an exclusive EU competence, and trade agreements are concluded by the Union alone. Other agreements may be concluded as mixed agreements requiring ratification by both the Union and Member States.
Secondary Law
Secondary legislation comprises the legal instruments listed in Article 288 TFEU: regulations, directives, decisions, recommendations, and opinions. These instruments are adopted by the EU institutions on the basis of legal bases in the Treaties and constitute the primary means through which EU law is enacted and implemented.
Regulations have general application, are binding in their entirety, and are directly applicable in all Member States. A regulation becomes part of national law without any implementing measure and creates rights and obligations for individuals that national courts must enforce. Regulations are used where uniform application of EU law across all Member States is essential, as in the Common Agricultural Policy, customs union, and competition law.
Directives are binding as to the result to be achieved but leave to the national authorities the choice of form and methods of implementation. Directives require transposition into national law within a specified period and give Member States discretion as to how to achieve the prescribed result. Directives have vertical direct effect after the implementation deadline where their provisions are sufficiently clear, precise, and unconditional (Van Duyn v Home Office, Case 41/74), but not horizontal direct effect between private parties (Marshall v Southampton Health Authority, Case 152/84).
Decisions are binding in their entirety on those to whom they are addressed. A decision may be addressed to a Member State, an individual, or an undertaking. Decisions are used for individual administrative acts, such as competition law decisions imposing fines on undertakings, and for certain legislative measures under specific Treaty provisions.
Recommendations and opinions have no binding force. They constitute soft law instruments that guide the interpretation of EU law and may be taken into account by national courts. Recommendations may have indirect legal effects, including the obligation of national courts to take them into consideration when interpreting national law (Grimaldi, Case C-322/88).
Delegated and Implementing Acts
Articles 290 and 291 TFEU establish a hierarchy within secondary law by distinguishing between legislative acts adopted under the ordinary or special legislative procedures, and non-legislative acts adopted by the Commission (or the Council in certain cases).
Delegated acts under Article 290 TFEU are acts of general application that supplement or amend certain non-essential elements of a legislative act. The legislature delegates to the Commission the power to adopt delegated acts, subject to limits on the scope and duration of the delegation. The essential elements of an area must be reserved for the legislative act and cannot be delegated. The delegation must be expressly defined as to objectives, content, scope, and duration, and is subject to control mechanisms: the legislature may revoke the delegation or object to a specific delegated act.
Implementing acts under Article 291 TFEU provide uniform conditions for implementing legally binding Union acts. Implementing acts are adopted where uniform implementation is necessary and are subject to the comitology system under Regulation (EU) No 182/2011. Member State representatives in committees supervise the Commission’s exercise of implementing powers through examination and advisory procedures. The distinction between delegated and implementing acts has generated litigation, with the CJEU clarifying that the decisive criterion is whether the act supplements or amends the legislative act (delegated) or provides uniform implementation (implementing) (Commission v Parliament and Council, Case C-427/12).
The Hierarchy of Norms
The hierarchy of EU law can be summarised as follows. At the highest level stands primary law: the TEU, TFEU, Charter of Fundamental Rights, and Protocols, which have constitutional status. Below primary law rank general principles of EU law as developed by the CJEU, which are unwritten sources of constitutional character. International agreements concluded by the Union rank below primary law but above secondary legislation. Secondary legislation — regulations, directives, and decisions — must comply with primary law, general principles, and international agreements. Within secondary legislation, legislative acts adopted under the ordinary or special legislative procedures rank above delegated acts, which rank above implementing acts.
This hierarchy is enforced through the system of judicial review available under Articles 263, 267, and 277 TFEU. Any EU act may be challenged for violating higher-ranking norms. National courts, through the preliminary reference procedure, may refer questions of validity to the CJEU. The hierarchy ensures that the EU legal order operates as a coherent system governed by the rule of law, with clear priorities and mechanisms for resolving normative conflicts.