In this blog post Alastair Holder Ross of Monckton Chambers discusses the Court of Appeal’s recent judgment in Merck Serono v Comptroller-General of Patents [2025] EWCA Civ 45, which clarifies the circumstances in which domestic courts will depart from assimilated EU case law post-Brexit.
The Court of Appeal’s recent judgment in Merck offers a helpful and timely summary of the principles that the Court of Appeal will apply when considering whether to depart from “assimilated CJEU case law”. As will be recalled, what was called “retained EU case law” in s.6(7) of the EUWA 2018 as enacted is now called “assimilated EU case law” as a result of the amendments made to the 2018 Act by the Retained EU Law (Revocation and Reform) Act 2023.
The Court took the question in two stages – whether it could depart from assimilated case law, and, assuming it could, whether it would have done so. This is the latest in a growing line of post-Brexit judgments on this topic, including TuneIn, Industrial Cleaning, and Thatchers (considered by Jack Williams in previous blog posts here, here and here). As a result of these judgments there is an increasingly settled body of authority on the approach to be taken by the Court.
First, the facts: the case concerned an application by Merck, a pharmaceutical company, for a Supplementary Protection Certificate (SPC) – an extension to patent protection. The application was rejected by the UK Intellectual Property Office (UKIPO) in reliance on the CJEU decision in Santen, a pre-Brexit case which continues to form part of domestic law as assimilated case law. Merck challenged the decision on the basis that Santen was wrongly decided. In Santen, the CJEU had overturned Neurim, an earlier case on the interpretation of the SPC Regulation. Merck argued that the correct approach to interpreting the Regulation had been taken in Neurim, and therefore Santen should not be followed.
Was the Court of Appeal entitled to depart from Santen?
The judgments of Birss LJ and Lewison LJ include helpful analysis of when domestic courts may depart from assimilated case law. The starting point is that assimilated case law remains binding on lower courts (including the High Court) post-Brexit.
The position in respect of the Court of Appeal is governed by the European Union (Withdrawal) Act 2018 (Relevant Court) (Retained EU Case Law) Regulations (SI 2020/1525). The Court of Appeal’s power to depart from assimilated case law derives from s.6(5A) of EUWA 2018 and s.6(4)(ba). By s.6(4)(ba) a “relevant court” defined in a statutory instrument made under s.6(5A) is not bound by any assimilated case law so far as provided for in that statutory instrument. SI 2020/1525 defines the Court of Appeal as a “relevant court” in paragraph 3(b) and paragraph 4 sets out the circumstances in which it will be bound.
Under paragraph 4(2) of SI 2020/1525, the Court of Appeal (being “a relevant court”) is bound by assimilated case law “so far as there is post-transition case law which modifies or applies that retained EU case law and which is binding on the relevant court”.
As Birss LJ explained, this means the Court of Appeal is only required to follow assimilated case law where (i) it has been applied (or “modified”) in a previous decision of the Supreme Court or Court of Appeal; (ii) the case law is applied as part of the ratio of that previous decision of those appellate courts; and (iii) none of the recognised exceptions (see below) apply. Importantly, a prior decision of the High Court applying assimilated case law would not prevent the Court of Appeal from exercising the power to depart. In simple terms, the usual domestic rules of precedent are maintained which limit the Court of Appeal’s ability to depart from one of its (or the Supreme Court’s) previous decisions but permit it to depart from the decisions of lower courts. The Explanatory Memorandum toSI 2020/1525makes it clear that the changes do not alter the existing rules of precedent between decisions of UK courts.
Lewison LJ’s judgment expands on when case law is considered to have been applied or modified (limb (i) above). The previous decision need not address the same “precise point” nor explicitly consider departure from assimilated case law. All that is required is for the previous decision to decide that the assimilated case law “was correct and stated the law” on the relevant point. As to limb (ii), Birss LJ suggested at paragraph 14 that one relevant way of determining the ratio of a decision was to consider (per R (Youngsam) v Parole Board [2019] EWCA Civ 229) whether the court’s conclusion “would be (much) weaker” without the application of the assimilated decision.
The limited exceptions to the usual rules derive from Young v Bristol Aeroplanes Co Ltd [1944] KB 718, which was reaffirmed by the House of Lords in Davis v Johnson [1979] AC 264, 328.. They allow the Court of Appeal to depart from otherwise binding precedent where:
- There are conflicting Court of Appeal decisions on the point; or
- A previous decision of the Court of Appeal cannot stand with a later decision of the Supreme Court; or
- The decision was given per incuriam, i.e. in ignorance of a statutory provision or other binding precedent “which would have compelled a different decision” (emphasis in original, per Lewison LJ in Merck, at paragraph 86).
In Merck, the Court of Appeal unanimously concluded that it was precluded from departing from Santen.
Crucial to the Court’s decision was the fact that Merck is not the first time that the Court of Appeal has considered the SPC regime in the aftermath of Neurim and Santen, the two contradictory CJEU authorities. In Newron Pharmaceuticals v Comptroller-General of Patents [2024] EWCA Civ 128, the Court of Appeal had followed Santen rather than Neurim.
Accordingly, Santen could not be departed from in Merck since, first, a previous Court of Appeal in Newron had applied Santen as part of the ratio of its judgment and, second, none of the Young v Bristol Aeroplanes exceptions applied. Specifically, Lewison LJ stressed that the per incuriam exception would not be met simply because a relevant authority had not been cited in the previous decision. Instead, the exception would only be met where that authority would necessarily have had a decisive impact on the outcome of that case had it been brought to the attention of the Court.
Would the Court have departed from Santen if it had been able to?
After concluding it was unable to depart from assimilated case law, the Court considered whether it would have done so if permitted.
Where assimilated case law has not been applied by the Court of Appeal or the Supreme Court, paragraph 4(2) of SI 2020/1525 isn’t in play. Rather, paragraph 5 requires the Court of Appeal to “apply the same test as the Supreme Court would apply in deciding whether to depart from the case law of the Supreme Court”.
This mirrors the approach to assimilated EU case law of the Supreme Court itself. Under s.6(5) of the EUWA 2018, the Supreme Court has the power to depart from assimilated case law on the same grounds as it can depart from one of its own precedents – in accordance with the principles of the Practice Statement (Judicial Precedent) [1966] 1 WLR 1234. That Practice Statement was initially intended to affect only the use of precedent in the House of Lords. The application of the Practice Statement has therefore been considerably expanded post-Brexit – it no longer simply sets out the approach of the House of Lords (and now Supreme Court) when departing from its own precedents but has been coopted as a guide to both the Supreme Court and the Court of Appeal in deciding whether to depart from assimilated case law.
Importantly (as noted by Lewison LJ at paragraph 72), the legal framework for departing from assimilated case law was due to change on 1 October 2024 as a result of amendments to s.6 EUWA 2018 made by the Retained EU Law (Revocation and Reform) Act 2023. However, the relevant section is not in force and the commencement order that was due to bring it into effect has been revoked. Those potential changes and the Government’s decision to postpone them have been considered by Jack Williams in a previous blog post here.
The Practice Statement itself sets out the test in the broadest terms – the court should depart from precedent “when it appears right to do so”. Birss LJ summarised the approach at paragraph 17 in Merck: “the court will be very circumspect in applying the Practice Statement, or, putting it another way, great caution is required”. It is therefore insufficient to depart from an earlier decision merely because the court might have decided the point differently.
The three concurring judgments in Merck provide a helpful quasi-checklist that the Court will consider in applying the test, which aligns with the Court’s earlier approach in TuneIn, Industrial Cleaning and Thatchers. There therefore now appears to be a largely settled approach to the application of the Practice Statement in the context of departing from assimilated case law.
Birss LJ suggested that, first, a litigant urging the court to depart from assimilated case law must demonstrate that “the criticisms levelled at the assimilated EU case law […] are justified”. If they are not, “then the application of the Practice Statement does not arise” (paragraph 18). A CJEU decision must therefore be wrong before the Court will depart from it. This was echoed in the judgment of Lewison LJ, who stated at paragraph 88 that “a decision that Santen was wrong is a necessary but not a sufficient reason to exercise the power to depart”.
Arnold LJ, in his concurring judgment, emphasised the height of that hurdle where assimilated case law interprets assimilated legislation (here, the SPC Regulation), and where that legislation has been relevantly unamended post-Brexit. In these circumstances, the Court should only consider departing from assimilated case law if it is “convinced that the Court of Justice’s interpretation is wrong”. This is because, in the premises, “the will of Parliament is that the legislation should continue to be harmonised with that of the EU”.
Having concluded that Merck’s criticisms of Saten were unsound, this was the end of the matter – there was no reason to depart from assimilated case law on the point.
If this first hurdle had been crossed, Birss LJ stated that he would go on to consider whether “this would be a proper case to depart” since the mere fact that the Court of Appeal had concluded the previous point was wrongly decided is insufficient. As my colleagues David Gregory and Khatija Hafesji set out in a previous blog, in making this assessment particular weight will be given to legal certainty. A range of factors will be considered however. In Merck, this included:
- Which interpretation reduces legal uncertainty (Birss LJ, paragraph 57). This accords with TuneIn per Arnold LJ at paragraph 83, and per Sir Geoffrey Vos MR at paragraphs 201-202, as well as Industrial Cleaning, per Arnold LJ at paragraph 86; and Thatchers, per Arnold LJ at paragraph 151.
- Which interpretation tends towards greater coherence and consistency (Birss LJ, paragraph 57; Lewison LJ, paragraph 96)
- The likelihood of the CJEU reversing the decision (Arnold LJ, paragraph 59). In TuneIn, in a similar vein, Arnold LJ suggested it would not be sensible to depart from one CJEU case and not later cases (paragraph 87). Likewise, in Industrial Cleaning a relevant factor was whether the decision in question was an isolated judgment or in accordance with wider case law and practice (paragraph 85).
- The extent to which the decision has been (persuasively) criticised by academics, judges or practitioners (Arnold LJ, paragraph 59; and Lewison LJ, paragraph 93). See also TuneIn per Arnold LJ at paragraphs 81-82 and Industrial Cleaning per Arnold LJ at paragraph 87; and Thatchers per Arnold LJ at paragraphs 149-150.
- In circumstances where the court is interpreting an international instrument, which interpretation furthers the aim of producing a uniform interpretation across jurisdictions (Lewison LJ, paragraph 94). This is in line with Arnold LJ’s judgment in TuneIn at paragraph 79, and Sir Geoffrey Vos MR’s judgment at paragraph 198, as well as Arnold LJ in Thatchers at paragraph 146.
- Whether there has been a relevant change in circumstances since the decision, including changes in public policy (Lewison LJ, paragraph 95). Although not explicitly stated, an indication by Parliament that it no longer willed the relevant legislation to be harmonised would fit under this factor (to which see Arnold LJ, paragraph 59 and Thatchers, per Arnold LJ, paragraphs 145-146).
As set out above, these factors either replicate or add to those considered in TuneIn, Industrial Cleaning and Thatchers, which additionally considered the following factors:
- That the more difficult the task of interpretation (including due to a lack of guidance) the greater deference should be given to the CJEU’s interpretation (TuneIn per Arnold LJ, paragraph 80), especially where the CJEU has greater experience of the issue (Industrial Cleaning, per Arnold LJ, paragraph 84).
- The extent to which the relevant point was a considered part of the CJEU’s judgment (Industrial Cleaning, per Arnold LJ, paragraph 82-83).
- The extent to which the CJEU’s decision on the relevant point unduly restricts the proper development of the law by frustrating the objectives of the relevant legislation (Industrial Cleaning, per Arnold LJ, paragraph 88)
Summary and conclusion
Merck provides a succinct statement of the approach the Court of Appeal will take when deciding whether to depart from assimilated EU case law. It will ask two questions: can it depart, and should it?
- The first question is whether the Court of Appeal or Supreme Court has previously applied the ratio of the assimilated decision. If so, the Court cannot depart unless one of the recognised exceptions from Young v. Bristol Aeroplanes applies. If not, then the Court is entitled to depart from the decision.
- The second question involves considering whether it is proper to depart from the decision. Not only must the Court be persuaded that the decision was wrong on the relevant point, but it will also consider the range of factors set out in TuneIn, Industrial Cleaning, Thatchers and now Merck.
As the line of cases considering the Court of Appeal’s post-Brexit power to depart from assimilated EU case law increases, the Court’s approach has been marked by striking consistency. Merck adds to that consistency and reinforces TuneIn, Industrial Cleaning and Thatchers. For now, the approach seems largely settled. Whether the Labour Government amends the applicable test in due course, either by commencing the previous Government’s amendments to the test or by introducing its own, remains to be seen.
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