UK Law Before Member State Courts: Marleasing Survives Brexit, But the Reasoning Barely Does

This post, which is cross posted on EU Law Live, was contributed by Dr Johannes Ungerer, who is a Senior Research Lecturer in the Faculty of Law, a Deputy Director of the Institute of European and Comparative Law, and an Associate Research Fellow of St Hilda’s College, University of Oxford.

The CJEU’s judgment in Crédit agricole Corporate & Investment Bank (Case C-350/24, see summary here) is striking: not because of the result, which was largely foreseeable, but because of the reasoning offered in support of it, or rather the lack of a convincing legal basis for that reasoning. The preliminary ruling was requested in 2024 by the French Cour de cassation. The judgment was delivered by the Grand Chamber recently, composed of fifteen judges, with Advocate General Kokott having given the Opinion.

The case is important because it addresses a practically significant question for Member State courts applying UK law where the relevant UK provision transposed an EU Directive. Must courts in the EU still apply the Marleasing approach and interpret UK law in light of the relevant Directive where the facts predate 31 December 2020, i.e. the end of the Brexit transition period?

The facts illustrate the problem neatly. The claimant entered into an employment contract in 2007 governed by ‘UK law’ and brought proceedings before a French Employment Tribunal in 2013, alleging discrimination since 2010. The relevant facts therefore all predated Brexit. The claimant relied on the Equality Act 2010, which had transposed Directive 2006/54/EC while the UK was still a Member State. The Brexit point arose only because the French proceedings have been lasting so very long. The question was therefore whether a French court, in proceedings initiated before Brexit and applying UK law after Brexit to facts predating Brexit, must still interpret that UK law in conformity with the Directive which it had transposed during UK membership.

The Court of Justice framed the issue as whether the Withdrawal Agreement had ‘called into question’ the Marleasing interpretation and reliance on the Directive where a Member State court applies UK law that transposed the Directive. That framing was unfortunate. The Withdrawal Agreement does not answer the question, as the Court itself recognised. It does preserve certain legal situations, including the continued application of EU choice-of-law and jurisdiction rules to previously concluded contracts and previously initiated proceedings. But those provisions explain only why UK law remained applicable and why the French courts retained jurisdiction. They say nothing about how that UK law is to be interpreted, or about whether the underlying Directive remains relevant. The Trade and Cooperation Agreement would perhaps have been a more natural place to look for post-transition EU-UK answers, but it does not help either and was not mentioned. Nor does the legal basis for the UK’s withdrawal from the EU, Article 50 TEU, provide an answer.

The Court nevertheless relied on the general spirit of the Withdrawal Agreement and the principle of legal certainty. It reasoned that the Agreement sought to preserve the stability of legal situations existing before the end of the transition period. It also invoked the protection of legitimate expectations and the prohibition of unfair retroactive effects. These are undoubtedly important principles. But they are too general to determine whether Marleasing interpretation continues to apply when a Member State court applies UK law after Brexit to pre-Brexit facts. The Court also observed that ignoring the Directive would seriously limit legal certainty and the effective implementation of equal treatment, especially for a claimant whose case had taken many years to be decided. That is true, but detriment alone does not explain why the Marleasing obligation necessarily continues: after all, what is the detriment to one party in adversarial proceedings is usually to the benefit of the other.

The result is therefore substantively plausible but doctrinally thin. The Court reaches the right answer, but largely by inference. There is no clear rule in the Withdrawal Agreement, Article 50 TEU or the relevant continuity provisions which dictates the outcome. Nor does the absence of an agreement between the EU and the UK to terminate EU law retroactively really resolve the matter, since nobody would have suggested such an agreement in the first place.

A stronger basis would have been to frame the issue as one concerning the duties of Member State courts as Member State courts. Where such courts apply rules which are or were transpositions of EU Directives, they should in principle interpret those rules in conformity with the relevant Directive. That reasoning would rest not on the benefits or detriments of doing so, nor on the current relationship between the EU and the legal system whose law is being applied, but on the supremacy and effectiveness of EU law within Member State courts, and on the objectives of Directives under Article 288 TFEU. It would also reflect the status of the EU legal order within the courts of the Member States.

That approach would, admittedly, raise difficult questions at the margins. What if the law of a former Member State had since been amended so substantially that it no longer resembled the transposing measure? What if the proceedings were initiated only after the duty to transpose had ceased? What if the relevant facts arose after the end of membership? What if the law of a non-Member State had voluntarily mirrored a Directive because of the ‘Brussels Effect’? These questions are real, but they should not obscure the core point: in a case like the one at hand, involving pre-Brexit facts, pre-Brexit proceedings and UK law that transposed an EU Directive while the UK was a Member State, the obligation of the Member State court is best explained positively by the role of EU law in Member State courts, not negatively by the absence of any rule saying otherwise.

This becomes even clearer when looking at the second referred question, exposing the same weakness from another angle. It concerned the application of the law of ‘another Member State’, although the case was about UK law as the law of a former Member State. In a genuinely intra-EU case, for example French courts applying German law that transposes a Directive, there would be little doubt that the law must be interpreted consistently with the Directive. But the Court’s reasoning proceeded largely as if that were still the situation here. It relied on the duties among Member States, mutual trust between Member States, and even mechanisms of judicial cooperation such as the European Judicial Network. This is awkward because the UK is no longer a Member State and such EU mechanisms are not available in the same way. The Court addressed that reality only very briefly in a single paragraph, essentially referring back to its answer to the first question.

The judgment should therefore be read as correct in outcome but not highly persuasive in reasoning. Its practical message is clear and sensible: where a Member State court applies UK law that transposed an EU Directive, and the relevant facts and proceedings predate the end of the transition period, the Member State court must continue to interpret the UK law in conformity with the Directive. But the doctrinal foundation remains underdeveloped. The better explanation would have openly acknowledged that the UK is now a non-Member State, while grounding the continuing interpretative obligation in the supremacy, effectiveness, and role of EU law in Member State courts. The Court reached the right destination, but by a route thinner than EU law in the face of Brexit deserves.