Sources and institutions of EU law

This first week is foundational. EU law is not merely a body of substantive rules about markets, citizenship, competition, or free movement. It is a legal order constituted by sources, institutions, procedures, and doctrines which determine how rules are made, who may make them, how they rank, and how they are enforced. A Cambridge answer on EU law normally turns on that architecture. If the architecture is weak, later topics become a list of rules without constitutional explanation.

The European Union is founded on treaties concluded by Member States. Those treaties create institutions, confer competences, prescribe legislative procedures, and generate legal norms. The principal treaties are the Treaty on European Union and the Treaty on the Functioning of the European Union. They are primary law. Beneath them are secondary acts, principally regulations, directives, and decisions, together with delegated and implementing acts. Alongside these sit general principles of EU law, the Charter of Fundamental Rights, international agreements concluded by the Union, and a large penumbra of soft law: recommendations, opinions, communications, guidelines, notices, and institutional practices.

The central institutional point is that the EU is neither a federal state in the orthodox sense nor an ordinary international organisation. It has law-making institutions, a court with compulsory jurisdiction in many fields, directly applicable legal instruments, and doctrines of supremacy and direct effect developed by the Court of Justice. Yet it remains a polity of conferred powers: the Union may act only within the competences attributed to it by the Member States in the treaties. This tension between constitutional autonomy and attributed competence is the organising theme of the subject.

For Cambridge Part IB purposes, this topic performs three functions. First, it supplies vocabulary: primary law, secondary law, direct effect, supremacy, competence, conferral, subsidiarity, proportionality, institutional balance, delegated acts, implementing acts, and retained EU law. Secondly, it supplies method: EU legal reasoning is often purposive, teleological, institutional, and systemic. Thirdly, it supplies a constitutional frame for Brexit. Although the United Kingdom has left the EU, EU law remains examinable because it shaped UK public and private law for nearly half a century; because retained EU law, now increasingly relabelled and reformed, continues to matter; and because comparative constitutional questions raised by EU law remain central to modern legal education.

The immediate aim is not to memorise every treaty article. It is to understand the hierarchy of sources, the allocation of functions among the institutions, and the Court of Justice’s role in transforming a treaty-based organisation into an autonomous legal order.

The European Union’s legal order emerged from the post-war project of economic integration. The European Coal and Steel Community was established in 1951; the European Economic Community and Euratom followed under the Treaties of Rome in 1957. The initial object was not a comprehensive constitutional state but sectoral and market integration. Yet the legal techniques used to secure that integration were unusually strong. The treaties created institutions with continuing powers, conferred jurisdiction on a supranational court, and required Member States to accept obligations capable of operating within domestic legal systems.

The early decades are dominated by two judicial moves. In Van Gend en Loos, the Court of Justice held that provisions of the EEC Treaty could confer rights on individuals enforceable before national courts. In Costa v ENEL, it articulated the primacy of Community law over conflicting national law. Those doctrines were not spelt out in the original treaty text in anything like their later constitutional form. They were derived from the nature, scheme, and objectives of the Community. The Court reasoned that the common market could not function if obligations were merely inter-state promises enforceable only through diplomatic or international mechanisms. National courts became ordinary courts of EU law.

Treaty revision then deepened and widened the project. The Single European Act 1986 strengthened the internal market programme and expanded qualified majority voting. The Maastricht Treaty 1992 created the European Union, introduced Union citizenship, developed economic and monetary union, and adopted a pillar structure. Amsterdam and Nice altered institutional arrangements and competences. The Lisbon Treaty, in force from 2009, abolished the pillar structure for most purposes, gave the Charter of Fundamental Rights the same legal value as the treaties, reformulated competences, and refined legislative procedures. Lisbon is the essential modern textual settlement for institutional law.

The history also includes enlargement. The Union moved from six original Member States to a much larger and more diverse polity. Enlargement increased the need for institutional manageability, majority voting, judicial coherence, and administrative coordination. It also sharpened questions of legitimacy. As legislative power shifted from unanimity among governments towards ordinary legislative procedure involving the European Parliament and Council, the democratic basis of EU law became a central theme.

The United Kingdom’s position was distinctive. It joined the Communities in 1973 through the European Communities Act 1972, which operated as the domestic conduit for Community law. UK courts accepted the effect of EU law within domestic law through that statute, most famously in Factortame. Following the 2016 referendum, withdrawal was effected under Article 50 TEU. The European Union (Withdrawal) Act 2018 repealed the 1972 Act and retained a large body of EU-derived law to avoid legal discontinuity. Later legislation has altered the status and terminology of retained EU law, but the basic point remains: a Cambridge student cannot understand modern UK law without understanding the EU sources from which much of it came.

Historically, therefore, EU law is a story of legal constitutionalisation. Economic treaties generated a judicially enforceable legal order; institutional reforms responded to expansion and legitimacy concerns; and withdrawal has forced domestic law to confront the afterlife of supranational norms.

The first principle is conferred competence. The Union has no general police power. It may act only within competences conferred by the Member States in the treaties. This distinguishes the EU from a sovereign state and gives legal form to Member State consent. Competence is not a peripheral technicality: it determines whether a measure is valid, which institution may act, what procedure must be used, and what standard of review will apply. EU competence is commonly described as exclusive, shared, or supporting, coordinating, and supplementing. Exclusive competence means that only the Union may legislate and adopt legally binding acts in the relevant field, save where Member States are empowered to do so. Shared competence means that Member States may act unless and until the Union has acted. Supporting competence does not permit harmonisation where the treaties exclude it.

The second principle is institutional balance. The treaties allocate functions among institutions: the Commission normally proposes legislation and guards the treaties; the European Parliament and Council legislate under ordinary legislative procedure; the European Council gives political direction; the Court of Justice ensures observance of law; the European Central Bank exercises monetary functions for the euro area; and the Court of Auditors supervises accounts. Institutional balance is not strict separation of powers. The EU is a compound constitutional structure in which executive, legislative, administrative, and judicial functions are deliberately interwoven. The doctrine prevents one institution from appropriating powers conferred on another and helps police the procedural legality of Union acts.

The third principle is legality and review. EU institutions must act within powers, observe essential procedural requirements, give reasons where required, respect fundamental rights, and comply with general principles such as proportionality, legal certainty, legitimate expectations, equality, and effective judicial protection. The action for annulment, preliminary reference procedure, infringement proceedings, and pleas of illegality form an integrated system of review. Les Verts is the classic authority for the proposition that the Community was based on the rule of law, in the sense that neither Member States nor institutions could avoid review of the conformity of their acts with the constitutional charter constituted by the treaty.

The landmark cases should be read as constitutional decisions about the nature of the EU legal order, not simply as authorities attached to isolated propositions. Van Gend en Loos is the starting point. A customs classification dispute produced a general doctrine: treaty provisions may confer enforceable rights on individuals. This transformed Member State courts into ordinary enforcers of EU law and shifted Community law away from the paradigm of diplomatic enforcement. The doctrine’s importance lies not merely in rights, but in institutional design. If individuals can invoke EU law, compliance no longer depends solely on Commission enforcement or inter-state action.

Costa v ENEL supplied the second pillar. The Court reasoned that Community law could not be overridden by subsequent domestic legislation without undermining the uniformity and effectiveness of the treaty system. In formal terms, this is supremacy. In constitutional terms, it is a claim about the autonomy of the legal order created by the treaties. The difficulty, which persists, is that national constitutional courts have not always accepted supremacy on identical terms. The Court of Justice grounds it in EU law itself; national courts often ground domestic acceptance in constitutional provisions or statutes.

ERTA is essential for institutional competence. It recognised implied external competence: where common internal rules have been adopted, Member States may be precluded from undertaking international obligations which affect those rules. The case illustrates the Court’s readiness to reason structurally from the effectiveness and coherence of Union action. It also shows that competence is not exhausted by express treaty words.

Les Verts is the rule of law case. The Court treated the treaty as a constitutional charter and insisted that institutional acts must be reviewable. Its enduring significance is methodological: gaps in textual standing or review structures may be interpreted in light of the requirement that public power be subject to legality. Later case law has not removed the restrictive standing rules for private applicants under Article 263 TFEU, but Les Verts remains the emblem of judicially articulated constitutionalism.

Meroni and Romano concern delegation. They show that institutions may not transfer discretionary powers in a way that disrupts the treaty allocation of responsibility. These cases became especially important as EU administration developed agencies and complex regulatory networks. Modern agency law is more flexible than a crude reading of Meroni might suggest, but the underlying concern persists: discretionary public power requires a treaty-compatible chain of accountability.

Kadi addresses the relationship between EU law and international law. The Court annulled EU measures implementing UN sanctions insofar as they infringed EU fundamental rights guarantees. This was not a denial of the importance of international peace and security; it was a statement that measures within the EU legal order must comply with its constitutional requirements. Kadi is therefore a leading expression of autonomy.

Pringle concerns institutional adaptation in crisis. The Court upheld the European Stability Mechanism and addressed the relationship between Member State action, EU competences, and treaty constraints. It is useful because it demonstrates the Court’s tendency to permit pragmatic institutional solutions while preserving the language of conferral and legal limits. Together, these cases establish the basic grammar of EU constitutional law: direct effect, supremacy, competence, review, delegation, autonomy, and institutional balance.

See practice questions section below.

See further reading section below.