EU law, Brexit, and the retained EU law regime

EU law supremacy in UK law was always a domestic constitutional choice, not a surrender of sovereignty. The European Communities Act 1972 made EU law part of UK law and gave it priority over conflicting statutes, but this was a rule of UK law that Parliament could revoke at any time. Factortame (No 2) established that courts could disapply Acts of Parliament conflicting with EU law, but only because Parliament had voluntarily accepted this limitation through the ECA. Thoburn refined this by classifying the ECA as a 'constitutional statute' immune from implied repeal—requiring express words to override—but still revocable. Brexit proved the principle: Parliament authorised withdrawal, repealed the ECA, and converted EU law into 'retained EU law' under domestic control. The Retained EU Law (Revocation and Reform) Act 2023 then removed EU law's special status entirely. Throughout, sovereignty remained with Parliament; membership was its exercise, not its abandonment.

R v Secretary of State for Transport, ex parte Factortame Ltd (No 2) [1991] 1 AC 603: Courts must disapply UK statutes conflicting with directly effective EU law because Parliament voluntarily accepted this limitation in the ECA 1972. This established the practical reality of supremacy while maintaining that it derived from domestic statute, not EU doctrine.

Thoburn v Sunderland City Council [2003] QB 151: The ECA is a 'constitutional statute' that cannot be impliedly repealed—only express words or necessary implication suffice. This reconciled continuing sovereignty with EU supremacy: Parliament bound itself through higher-order entrenchment but retained power to unbind expressly.

R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5: Triggering Article 50 required an Act of Parliament because withdrawal would remove statutory rights created by the ECA. This reaffirmed that EU rights existed by virtue of UK statute and that prerogative cannot frustrate statutory schemes.

Macarthys Ltd v Smith [1979] ICR 785: If Parliament used express words to legislate contrary to EU law, courts would follow Parliament. This preserved ultimate sovereignty even at the height of integration.

Courts approach EU/retained EU law through distinct temporal regimes. During membership (pre-2020): Apply supremacy via ECA s.2(4)—EU law prevails unless Parliament legislates expressly to contrary. Use Marleasing principle to interpret UK law consistently with directives where possible. Post-Brexit transition (2020-2023): Apply retained EU law under EUWA 2018—supremacy continues for pre-exit conflicts only; interpret using pre-exit CJEU case law but Supreme Court/Court of Appeal can depart if 'right to do so'. Post-REUL 2023: Retained EU law assimilated into ordinary domestic law—no special status, standard interpretation rules apply, normal implied repeal operates. For Northern Ireland, Windsor Framework maintains limited EU law application for goods/customs. Key test throughout: did Parliament expressly authorise departure from EU obligations? If not, apply relevant regime's rules. Always distinguish between EU's view of supremacy (inherent/absolute) and UK's view (statutory/revocable).

Conflating EU and UK supremacy doctrines: Students state 'EU law is supreme' without specifying perspective. EU doctrine (Costa) sees supremacy as inherent; UK doctrine (Factortame) sees it as voluntary statutory choice. Always specify whose account you're using.

Missing the REUL 2023 changes: Answers discussing retained EU law without noting 2023 reforms are outdated. The special status is gone—retained law is now ordinary domestic law.

Misreading Thoburn: Constitutional statutes cannot be impliedly repealed, not that they cannot be repealed at all. Parliament could always repeal the ECA expressly (and did).

Overstating sovereignty loss: Never say sovereignty was 'transferred' or 'surrendered'—courts consistently held it was voluntarily limited but retained. Use precise language about temporary limitations, not permanent transfers.