Introduction
The United Kingdom’s withdrawal from the European Union has resulted in a fundamental change to the UK’s legal and constitutional landscape. A central issue in this new arrangement is the status of the vast body of law derived from the UK's 47-year membership of the EU. The European Union (Withdrawal) Act 2018 (EUWA 2018) was enacted to provide a framework for legal continuity, preserving most EU law as it existed on exit day and incorporating it into domestic law as "retained EU law". This body of law is extensive, particularly in areas such as employment, consumer, and environmental rights, where EU directives and regulations have historically provided a foundation for domestic protections.
A key element of retained EU law is the case law of the Court of Justice of the European Union (CJEU), which provided authoritative interpretations of EU law. The question of whether UK courts should continue to be influenced by this jurisprudence is one of the most significant post-Brexit legal debates. This essay will argue that while the political objective of Brexit was to re-establish judicial independence, there are compelling reasons for UK courts to continue to rely on retained EU case law. The essay will suggest that the benefits of legal certainty, the protection of established rights, and the interconnected nature of the retained law outweigh the arguments for a rapid departure. However, the new powers granted to the courts by the Retained EU Law (Revocation and Reform) Act 2023 mean that a gradual divergence is now inevitable.
The Evolving Legal Framework
The initial approach to retained EU law was established by the EUWA 2018, which aimed to create a stable transition by freezing EU law in the domestic system at the moment of exit. Section 2 of the Act preserved EU-derived domestic legislation, direct EU legislation, and other rights and principles. Crucially, section 6 dealt with the interpretation of this new body of law. Section 6(3) stated that pre-exit principles and decisions of the CJEU would continue to be binding on UK courts, with the exception of the Supreme Court and the Court of Appeal. These senior courts could depart from retained EU case law when it was "right to do so" (s 6(5)), a test analogous to that used by the Supreme Court when departing from its own past decisions (Practice Statement [1966]). This created a high bar for departure, prioritising stability and certainty.
This position has been significantly altered by the Retained EU Law (Revocation and Reform) Act 2023 (REUL Act 2023). While the Act's most controversial "sunset clause", which would have automatically revoked most retained EU law, was removed, it has introduced major changes to the doctrine of precedent. The Act rebrands "retained EU law" as "assimilated law" (s 5). More importantly, section 6 introduces a new, lower test for the Supreme Court and Court of Appeal to depart from pre-exit CJEU case law. Courts must now consider factors such as the fact that CJEU decisions "are not decisions of a United Kingdom court" and may depart from a precedent if they consider it "appropriate" to do so. This change signals a clear legislative intention to encourage greater judicial divergence from the EU's legal legacy (UK Parliament, 2023).
The Case for Continued Reliance
Despite the new legislative framework encouraging divergence, there are strong arguments for UK courts to exercise caution and continue to rely on the existing body of retained EU case law, particularly in the key areas of employment, consumer, and environmental rights.
The most significant argument is the need for legal certainty. For decades, businesses, employers, workers, and public bodies have organised their affairs based on a legal framework shaped by CJEU jurisprudence. In employment law, for instance, complex rules governing holiday pay and working time, originating from the Working Time Directive, have been clarified almost exclusively by a long line of CJEU cases (e.g. Federación de Servicios de Comisiones Obreras v Deutsche Bank SAE [2019] EUECJ C-55/18 on recording working hours). To suddenly disregard this case law would create a legal vacuum, generating immense uncertainty and encouraging costly and protracted litigation as parties seek to test the boundaries of the new "assimilated law" (Barber, 2023). For businesses, this uncertainty acts as a barrier to investment and planning. For individuals, it makes accessing and enforcing their rights more difficult and unpredictable.
Secondly, continued reliance is important for maintaining the current level of protection for individuals. EU law has often been described as providing a "floor" of minimum rights across member states. In many instances, the CJEU adopted a purposive, rights-focused interpretive approach that expanded the scope of these protections. For example, in consumer law, the CJEU's broad interpretation of "unfair terms" under the Unfair Contract Terms Directive has been instrumental in protecting consumers from one-sided contracts. Similarly, in environmental law, the CJEU’s jurisprudence on directives concerning habitats and air quality has empowered citizens and NGOs to hold governments to account. A departure from this case law could be seen by courts as a signal to adopt a more restrictive interpretation of these rights, potentially leading to their dilution and a "levelling down" of standards (Lock, 2021).
Finally, retained EU law is a complex, interconnected system. A single CJEU judgment often relies on a network of related principles and previous decisions. For a UK court to depart from one ruling without fully considering the systemic implications could lead to legal incoherence. As noted by Chalmers et al. (2019), EU law developed as a distinct legal order with its own interpretive maxims. A piecemeal departure by UK courts, which may not have the same institutional perspective as the CJEU, risks creating contradictions and inconsistencies in the domestic law that was intended to be preserved as a functioning whole.
The Case for Divergence
Conversely, there are powerful constitutional and legal arguments for UK courts to move away from retained EU case law. The primary political driver of Brexit was the restoration of parliamentary and judicial sovereignty. Proponents of divergence argue that as long as UK courts feel bound by the decisions of a court belonging to a political entity that the UK has left, full sovereignty has not been achieved. The Lord Chief Justice, Lord Burnett, has noted that leaving the EU provides the UK’s common law with an opportunity for development "in a different way" (House of Lords, 2020, p. 11). The REUL Act 2023 can be seen as Parliament giving the judiciary explicit permission to forge this new path and develop a distinctively British jurisprudence free from the influence of the CJEU.
Furthermore, there is a distinct difference in interpretive methodology between UK courts and the CJEU. The CJEU famously employs a teleological, or purposive, method of interpretation, where legal texts are interpreted in light of the aims and objectives of the EU Treaties (Craig and de Búrca, 2021). This can sometimes lead to outcomes that appear to go against the literal wording of the law. UK courts, by contrast, have traditionally placed more emphasis on literal and grammatical interpretation. Continuing to follow CJEU case law would require UK judges to perpetually engage with a legal methodology that is arguably alien to the common law tradition. Divergence would allow them to return to more familiar interpretive tools when dealing with the statutory footing of assimilated law.
Another practical problem with continued reliance is that retained EU case law is now a static body of law, frozen at the end of the transition period on 31 December 2020. The law in the EU continues to evolve, with the CJEU handing down new judgments that clarify or develop legal principles. UK courts relying on the pre-2021 case law will be working with an increasingly outdated and incomplete legal picture. This could lead to a situation where UK law becomes ossified, unable to respond to new social, technological, or economic challenges in the way that the living law of the EU can. Therefore, divergence is not just desirable but necessary to prevent the law from becoming stale.
Conclusion
The question of whether UK courts should continue to rely on retained EU case law presents a deep conflict between the political desire for constitutional renewal and the practical requirement for legal stability. The arguments for divergence – founded on sovereignty and the need for the law to evolve – are constitutionally significant. The new powers under the REUL Act 2023 make it clear that Parliament expects the senior courts to begin this process of developing a separate body of UK law.
However, a rapid and wholesale departure from decades of established jurisprudence in fundamental areas like employment, consumer and environmental rights would be a mistake. The cost in terms of legal uncertainty, the potential for weakening hard-won rights, and the risk of creating legal incoherence is too high. The established case law provides a predictable and stable foundation that benefits both businesses and individuals.
Therefore, UK courts should not abandon reliance on retained EU case law but should instead adopt a cautious and incremental approach. The new power to depart where "appropriate" should be used sparingly, reserved for cases where a CJEU ruling is manifestly unworkable in the UK context or where there is a clear and pressing need to develop a different legal solution. In the short to medium term, continued reliance provides a necessary bridge from the old legal order to the new, ensuring that the promise of legal continuity made in 2018 is not undermined. The challenge for the UK judiciary will be to balance the political mandate for change with its traditional role as a guardian of certainty, consistency, and the rule of law.
References
Barber, N. (2023) The Retained EU Law Bill: A Constitutional Charade? [Online] UK Constitutional Law Association Blog. Available at: https://ukconstitutionallaw.org/2023/01/23/nick-barber-the-retained-eu-law-bill-a-constitutional-charade/ (Accessed: 15 August 2023).
Chalmers, D., Davies, G. and Monti, G. (2019) European Union Law: Text and Materials. 4th edn. Cambridge: Cambridge University Press.
Craig, P. and de Búrca, G. (2021) EU Law: Text, Cases, and Materials. 7th edn. Oxford: Oxford University Press.
Federación de Servicios de Comisiones Obreras (CCOO) v Deutsche Bank SAE (Case C-55/18) [2019] EUECJ C-55/18, [2019] IRLR 656.
House of Lords, European Union Committee (2020) The European Union (Withdrawal) Act 2018 and the rule of law on and after exit day. HL Paper 14, 28th Report of Session 2019–21.
Lock, T. (2021) ‘The Future of Retained EU Law’, King's Law Journal, 32(2), pp. 263-275.
Practice Statement (Judicial Precedent) [1966] 1 WLR 1234.
UK Parliament (2023) Retained EU Law (Revocation and Reform) Act 2023. Available at: https://www.legislation.gov.uk/ukpga/2023/28/contents/enacted (Accessed: 15 August 2023).
