A Game of Judicial Tennis: The Supreme Court in Mercer

by | May 9, 2024

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About Ross Guinea McIntyre

Ross Guinea McIntyre works as a paralegal at a leading set of barristers’ chambers in London. He holds a Bachelor of Civil Law (BCL) from the University of Oxford, and a BA (Hons) in Law from the University of Cambridge. His research interests lie in international and comparative human rights law, criminal law, administrative law, and legal philosophy.

The Supreme Court has once again considered the proper scope of sections 3 and 4 of the Human Rights Act 1998 (HRA), this time in relation to an employer’s response to an employee’s participation in industrial action. The history of these proceedings and the divergent opinions of each of the lower courts highlight the profound disagreement over when these provisions may be legitimately deployed. While the Supreme Court’s judgment goes some way in rebutting democratic concerns about declarations of incompatibility issued under section 4 HRA, it offers limited guidance on the proper application of the interpretive rule in section 3 HRA.


Section 146 of the Trade Union and Labour Relations (Consolidation) Act 1992 (TULRCA) protects a worker from ‘detriment’ imposed as a result of ‘taking part’ in trade union activities. Domestic courts have previously held that section 146 TULRCA does not extend to participation in industrial action (see Drew). The claimant suggested that she had been subjected to a detriment by being suspended and disciplined after participating in certain strikes. The Court had to consider whether the claimant’s Article 11 ECHR right to freedom of assembly and association had been violated, and, if so: (i) whether it could apply the ‘interpretive obligation’ under section 3 HRA to interpret section 146 TULRCA as providing protections to those participating in industrial action; or, if not (ii) whether it should issue a declaration of incompatibility under section 4 HRA.

The Court of Appeal, departing from the decision of the Employment Appeal Tribunal, declined to use either sections 3 or 4 HRA, invoking the traditional mantra of judicial restraint: leave it to Parliament to decide. The claimant appealed to the Supreme Court, whose judgment was handed down on 17 April 2024.

The Supreme Court’s decision in Mercer

As to the first issue, the Supreme Court, upholding the Court of Appeal, concluded that it was not possible to use section 3 HRA to give section 146 TULRCA a Convention compatible interpretation. There was no single legislative solution that would strike the appropriate balance between the rights of the employer and the rights of the worker in such a sensitive context. Extending the scope of section 146 TULRCA would “amount to impermissible judicial legislation rather than interpretation[102] and create a stark inconsistency between two identically worded provisions, thus undermining the internal coherence of TULRCA [108].

As to the second issue, the Supreme Court allowed the appeal and made a declaration of incompatibility under section 4 HRA. There was no good reason for rejecting the remedial measure provided for by that provision [120]. The claimant was not complaining of a mere ‘lacuna’ in the law, as the Court of Appeal had suggested, but of the effect of section 146 TULRCA, which legitimised detriments short of dismissal and therefore undermined her Article 11 right. This was not a case where it would be inappropriate to make a declaration of incompatibility. The fact that the ultimate legislative solution to the problem required Parliament to carefully consider a number of legislative solutions was a reason in favour of making a declaration, not a reason for refusing one [120].


In many ways, the Supreme Court’s judgment in Mercer is to be welcomed as an accurate and considered application of the law. In particular, the Court offers a welcome corrective to those concerned that declarations of incompatibility may be democratically suspect (see, for example, the majority judgment in Nicklinson). As the Court correctly notes, a declaration of incompatibility does not tell Parliament what to do. Instead, it merely puts Parliament on notice that an incompatibility requires addressing.

However, these proceedings demonstrate that oft-cited constraints on the use of section 3 HRA (see Sheldrake at [28]) provide little guidance to the courts that are tasked with applying them. The vagueness of these formulations leads the lower courts to divergent conclusions as to the strength of section 3 HRA. This is highlighted by the ‘judicial tennis match’ that took place in this case, where the Employment Appeal Tribunal took a far more expansive approach to the interpretive obligation than either the Employment Tribunal or the Court of Appeal. The Supreme Court’s judgment does little to assist the situation. This gives rise to rule of law concerns, in particular if individuals are unable to ascertain in advance whether they will fall within the protections afforded by a particular legislative provision.

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