Jefferi Hamzah Sendut: The Prorogation Case: Proportionality in All but Name?

The place of proportionality review in UK administrative law has been the subject of considerable doctrinal debate. This post argues that the Supreme Court’s Cherry/Miller (No 2) judgment should be understood as an application of proportionality as a common law ground of substantive review. Proportionality review is no longer confined to cases involving the Human Rights Act (HRA) 1998 (e.g. Miss Behavin’), European Union (EU) law (e.g. Lumsdon), or substantive legitimate expectations (e.g. Paponette).

Previous cases, in particular UNISON, mean it is appropriate to describe Cherry/Miller (No 2) as standing for the proposition that prerogative powers cannot be used to disproportionately interfere with fundamental constitutional principles. The Court’s treatment of the issues of the substantive effect of the exercise of prerogative power and the justificatory burden of proof are also characteristic of proportionality review.

The Court’s judgment

The Court unanimously held in Cherry/Miller (No 2) that the UK Prime Minister’s decision to advise the Crown to exercise the royal prerogative to prorogue Parliament from early September until 14th October 2019 was justiciable, and unlawful.

The Court framed its approach as concerned with whether the Prime Minister exceeded the scope of the prerogative power to prorogue Parliament. The ability of courts to make such determinations as to the scope of prerogative powers is uncontroversial (para 35). The Court thereby avoided questions of the justiciability of a “mode of exercise of the prerogative power within its lawful limits” (para 52).

The Court expounded on two fundamental constitutional principles, those of Parliamentary sovereignty, and the Parliamentary accountability of the executive (paras 41, 46). Both these principles would be unacceptably abrogated were the Court to recognise an unlimited prerogative power of prorogation. They thereby limited the power’s scope (paras 42, 48). Any prorogation decision which frustrated Parliament’s constitutional role without reasonable justification was unlawful (para 50).

“Four corners” review and proportionality

The Court’s express language does not countenance substantive review, whether via proportionality or Wednesbury irrationality review. Rather than “involving itself in the superintendence of the exercise of the power”, a traditional marker of substantive review, the Court’s decision held that there was “no sufficient [prorogation] power in the first place”.

However, the Court’s reference to UNISON indicates that this distinction is no obstacle to understanding Cherry/Miller (No 2) as an instance of proportionality review. In UNISON, Lord Reed on behalf of the Court held that a statutory provision empowering the Lord Chancellor to set tribunal fees had to be interpreted in light of the principle of legality. Parliament was presumed not to have authorised an interference with the fundamental right of access to justice beyond what was reasonably necessary to achieve a legitimate aim (para 88).

Lord Reed cautiously referred to his reasoning in UNISON as merely analogous to proportionality review as practiced in European Court of Human Rights jurisprudence (para 89). But his comments must be read in the context of his earlier judgment in Pham. There, Lord Reed took the view that UK administrative law recognised “in substance, a requirement of proportionality” (para 119). Importantly, this position was premised on precisely the application of the principle of legality he would subsequently utilise in UNISON, as is evident for two reasons.

First, in both Pham and UNISON, Lord Reed’s reasoning rests on the notion of implied limitations to statutory powers (Pham at para 118, UNISON at para 88). Second, ascertaining these limitations involved the assessment of the necessity of a measure in light of its effects in interfering with a fundamental right (Pham at para 119, UNISON at para 80).

Cherry/Miller (No 2) represents an endorsement of this species of proportionality review. The Court effectively reasoned by analogy from the treatment of the statutory power in UNISON to review an exercise of the prerogative (para 49), again through an application of the principle of legality. Both UNISON (at paras 89-90) and Cherry/Miller (No 2) (at paras 51, 57) saw the open-texture judicial evaluation of the substantive effects of the specific exercise of powers, in order to determine whether the scope of the powers had been transgressed (c.f. Paul Daly’s post on Cherry/Miller (No 2), which makes a similar observation).

In UNISON, a decision to exercise a statutory power in a manner leading to a disproportionate interference with a fundamental right was unlawful because the power’s scope was limited by presumed Parliamentary intention to only encompass proportionate exercises. Likewise, in Cherry/Miller (No 2), a decision to exercise a prerogative power in a manner leading to a disproportionate interference with fundamental constitutional principles was unlawful because the power’s scope was limited by the principles themselves to only encompass proportionate exercises.

Cherry/Miller (No 2) thereby confirms the suggestion in Youssef that common law proportionality review is applicable to exercises of prerogative powers (paras 56, 59), and the suggestion in Pham that proportionality review applies to measures impacting fundamental legal norms beyond individual rights (para 98).

Viewed in toto, Lord Reed has thus developed a species of proportionality review which straddles the boundary between “four corners” and substantive review. Contrast the classic “four corners” approach taken in Fire Brigades Union, which laid down a bright-line limit on the scope of prerogative powers: they cannot “frustrate the will of Parliament expressed in a statute” (at 552). Beyond the binary inquiry as to whether the prerogative was used in that way, questions of effect (and hence proportionality) were irrelevant.

The structure of proportionality review

True enough, Cherry/Miller (No 2) does not employ the paradigmatic four-stage structure of proportionality review demonstrated in HRA 1998 cases. A court ordinarily determines whether a (i) sufficiently important objective is being pursued by (ii) a rationally connected and (iii) necessary measure, (iv) in a manner which fairly balances the individual right (or in Cherry/Miller (No 2) a constitutional principle) interfered with and the community interest (Bank Mellat (No 2)), para 20).

But the structure’s absence can be reconciled with a characterisation of Cherry/Miller (No 2) as an instance where common law proportionality review was conducted, for two reasons. First, Lord Reed in Pham stated that where common law proportionality is applied, it is “less formally structured” than in HRA 1998 cases (para 118). Second, the steps of the paradigmatic proportionality enquiry can be identified within the Court’s judgment.

Steps (i) and (ii) were satisfied by the government’s pursuit of the objective of ushering in a new legislative agenda (paras 17, 51). However, the Court was not convinced that the Prime Minister’s exercise of the prerogative cleared the “necessity” (step (iii)) or “fair balance” (step (iv)) hurdles, even after according him deference (para 51). The necessity of the prorogation was not made out due to a failure to consider the alternative of a Parliamentary recess (para 60), and a fair balance was not struck due to its unjustified length (paras 60-61).

The burden of proof

Finally, conceiving of Cherry/Miller (No 2) as an instance of proportionality review explains why the Court so readily placed the burden of justification onto the Prime Minister (para 51). The burden of proof “shifts explicitly in proportionality [re]view. Once a violation of a protected interest is demonstrated, the burden is placed on the state to justify the interference.”


Cherry/Miller (No 2) is a development of previous proportionality review jurisprudence. The judgment confirms, albeit obliquely, previous judicial suggestions that UK administrative law recognises proportionality review as a common law ground of substantive review applicable beyond cases concerning the HRA 1998, EU law or substantive legitimate expectations. It also illustrates the applicability of proportionality review to exercises of prerogative power, and in safeguarding fundamental constitutional principles.

The judgment leaves persistent questions unanswered. It remains to be seen how the boundary between proportionality and Wednesbury irrationality cases should be policed. It is also unclear whether UK administrative law will continue to see the proliferation of the relatively unstructured species of proportionality review the Court employed. Such a course may be open to criticism on the grounds that it would forego the clarity a four-stage test offers.

Nevertheless, if these questions are adequately addressed in future, the wider application of common law proportionality review presents an opportunity to shore up substantive review’s legitimacy. In public law adjudication, courts will often have to make what are, in the broadest of senses, value-laden “political” determinations. Recognising this need not undermine the necessity of respect for authoritative judicial pronouncements. But UK administrative law would benefit from a doctrinal tool which allows these determinations to be made in a predictable and transparent manner.

Jefferi Hamzah Sendut is a law graduate from St John’s College, University of Cambridge, and a Master of Laws candidate at the London School of Economics and Political Science.

(Suggested citation: J. Hamzah Sendut, ‘The Prorogation Case: Proportionality in All but Name?’, U.K. Const. L. Blog (8th Oct. 2019) (available at