Theodore Konstadinides, Noreen O’Meara and Riccardo Sallustio: The UK Supreme Court’s Judgment in Miller/Cherry: Reflections on Its Context and Implications

On 24 September, the UK Supreme Court unanimously ruled that the Prime Minister’s advice to prorogue Parliament was unlawful, and that the resulting Order in Council and subsequent prorogation were ‘null, void and of no effect’. The litigation on the justiciability of prorogation and the lawfulness of the Prime Ministerial advice has led to one of the most engaging constitutional cases of recent times. As observers at the High Court and Supreme Court hearings, this post considers the context of the ruling, and certain striking implications of the judgment for the current and future Prime Ministers.

Prorogation litigation and backlash

It is well-known that this is an extraordinary case with extraordinary facts. The launch of parallel litigation in London and Edinburgh was conducted in the midst of reports threatening the courts not to ‘interfere’ in allegedly political territory, ministerial statements suggesting that members of the public fear the courts may not be independent, and most strikingly – reports that the Prime Minister may have been prepared to ignore the Supreme Court’s ruling.

Against that background, the Supreme Court should be credited for the transparency with which it made the hearing genuinely accessible to the public, and for its fast arrangements to hear the case outside of the legal term. Whilst the rhetoric noted above was toned down during the Supreme Court hearing (the Prime Minister confirming he would respect the outcome), the surrounding political and media speculation has been replete with messaging which suggested gaps in the commitment of the government and its ministers to respect the rule of law. Since the judgment, leaked Cabinet call comments have described the ruling as a ‘constitutional coup’ and ‘overthrowing the constitution’, while the Prime Minister’s own reaction in Parliament declared the court was ‘wrong to pronounce on what is essentially a political question at a time of great national controversy’. There is an important difference between reasoned disagreement and a disturbing failure to respect judicial independence. Some reactions from the heart of government have fallen into the latter, constitutionally irresponsible category.

Fundamental constitutional principles

The Supreme Court stayed focused on two issues: the scope of prerogative powers and parliamentary sovereignty. In order, however, to consider the court’s power to review the exercise of prerogative powers, it had to deal with the question of justiciability, a point which determined the High Court’s negative judgment in Miller v the Prime Minister.

In contrast with the High Court’s overly broad vision of what is non-justiciable, and the arguments advanced by the government that justiciability comes first as a matter of logic and law, the Supreme Court had no difficulty finding the matter justiciable. In the Supreme Court’s view, all prerogative powers are determined by common law.  The adjudication of legal questions – in this case, the scope of the prerogative power – is clearly justiciable. In this respect, the Supreme Court followed the argument of the fifth intervener (Deok Joo Rhee QC and Catherine Dobson acting on behalf of the Shadow Attorney General) which focused on the existence and extent of prerogative powers rather than the effect of exercising a prerogative. Their argument was predicated on the assumption that the Miller/Cherry case is indistinguishable from cases related to the impact of exercise of the power on particular individuals. A toned-down version of the Rhee and Dobson argument was inherent in the common position taken by Lord Pannick QC (acting for Miller), Aidan O’Neill QC (acting for the Scottish petitioners) before the lower courts, that justiciability cannot be assessed in isolation, but it should be integrated with consideration of the legal merits of the case. Having confirmed justiciability, it moved on to decide whether the Prime Minister’s advice was lawful by considering the effects of the prorogation and the quality of justification offered for the outcome. In the light of the principle of legality, if the prorogation had the effect of a serious restriction on parliamentary sovereignty and parliamentary accountability by frustrating Parliament’s constitutional functions, without reasonable excuse, then it would be beyond the scope of the prerogative power of prorogation.

As regards the scope of the Prime Minister’s prerogative power, the Court’s focus on this cut through the debate on political terrain. Para 39 summarises the position of the Court: […] the boundaries of a prerogative power relating to the operation of Parliament are likely to be illuminated, and indeed determined, by the fundamental principles of our constitutional law. The Court here uses constitutional language to describe the duty owed by the executive to Parliament. Prorogation must be legally justified by constitutional propriety. A due obedience justification is vested in constitutional principles of common law inclusive of a wider and legally enforceable concept of Parliamentary Sovereignty.

We know from Miller (No. 1) that prerogative power cannot be exercised incompatibly with the discernible will of Parliament. It is likewise clear from the Miller/Cherry judgment that no Prime Minister can undermine parliamentary sovereignty by preventing Parliament from exercising its power for as long as s/he pleases. As Lord Sumption remarked on BBC Radio 4, the problem was that the government sought to undermine the democratic legitimacy of public decision-making. According to the Court, tendering unlawful advice to the monarch to deprive the institution upon which rests the ultimate legislative authority in the UK from these functions amounts to offending action and must be judged by courts. The protection offered by the Court against threats posed to parliamentary sovereignty by the use of prerogative powers dovetails with strengthening another constitutional concept: the Prime Minister’s accountability to Parliament (para 33). Accordingly, the power to prorogue is limited by constitutional principles it would conflict with.

The Court’s approach to identifying whether a ‘reasonable justification’ for a five-week prorogation had been provided in the evidence was instructive. During the hearings, much attention was placed on the Prime Minister’s comments on Sky News when prorogation was announced, and on prior (now infamous) Downing Street memoranda, one of which included the Prime Minister’s view that a parliamentary sitting in September was a ‘rigmarole’, and that the plan to prorogue was not ‘especially shocking’. While those statements made headlines, it is the Supreme Court’s complete dismantling of a Da Costa memo (para 60), in the light of the Prime Minister’s comments, informed by the ‘unchallenged’ evidence from Sir John Major, which led the court to conclude that Boris Johnson had not fulfilled his ‘constitutional responsibility’. In this respect, para 60 should serve as a useful reference point for Prime Ministers when seeking prorogation. In the event that a longer-than-usual prorogation is sought in the future (for more than the average 4-6 day period foreseen by the Supreme Court), greater scrutiny of the rationale can be applied.

While the Court placed emphasis on the effect of prorogation on parliamentary sovereignty and the government’s accountability to Parliament, it did not expressly touch upon the issue of fundamental rights. There are two fundamental rights dimensions in Miller/Cherry which were raised by the appellants and interveners: first, that the sovereignty of Parliament is also a core justification for protecting the rights of individuals to access to courts (as per Lord Pannick’s submission); second, that Brexit has exposed gaps in the protection of EU-law derived fundamental rights (as per O’Neill’s submission) and of fundamental rights protected under the Good Friday Agreement (as per Ronan Lavery QC, acting for Raymond McCord).

The first dimension was not expressly addressed by the Court simply because the Court did not feel constrained by the logic applied previously by the High Court that a decision on the question of justiciability of prerogative powers shall only take place where questions do not arise in a statutory context or which affect individual rights.

As regards the second dimension, while the Court’s objective was to keep strictly focused on the direct legal effects of prorogation, the judgment impliedly confirmed Aidan O’Neill’s observation that the exercise of Parliament’s functions was also essential because Parliament, in accordance with the principle of legality, needs to give a prior statutory authority, whether expressly or by any necessary implication, to pursue a policy of no deal Brexit.  In para 57 the Court stressed that it is “indisputable” that “the House of Commons as the democratically elected representatives of the people, has a right to have a voice in how [the constitutional] change [caused by Brexit] comes about …”, also in consideration of the House of Commons having already “demonstrated by its motions against leaving without an agreement and by the European Union (Withdrawal) (No 2) Act 2019, that it does not support the Prime Minister [on a no deal Brexit]…” and “that it is especially important that he be ready to face the House of Commons.” In other words, we can deduct from the judgment that in the event of a no deal, Parliament would have a statutory duty to perform and express its will and that such will should, therefore, form part of the ‘constitutional requirements’ under Article 50 TEU.

Implications of the ruling for the Prime Minister

So we return once again to the realm of Brexit and action-packed politics, with a vote of no confidence or a motion for contempt of Parliament possible (despite speculation, the prospect of MPs delving into the first edition of Erskine May to impeach the Prime Minister are remote in the extreme). The legislative agenda thought to have fallen on 10 September continues, questions posed by MPs before that date should be answered.

Miller/Cherry will have implications for future prime ministerial conduct (or executive conduct) in several ways. First, as the Prime Minister was found to have frustrated the role of Parliament without justification there is an unwritten expectation that he must not prorogue Parliament unless he does so in a constitutionally orthodox manner. Second, the Supreme Court’s judgment is a caution for the Attorney General and Prime Minister (and for any future holders of his office) about the scope of this prerogative power. Third, as noted above, the court’s failure to identify ‘any reason – let alone a good reason’ (para 61) for advising the Queen to prorogue will be recalled if an apparently unorthodox prorogation is sought in the future. The judgment provides cover for scrutinising such decisions more closely.

The Supreme Court has made an inevitable decision, grounded in classic constitutional and legal principles. From now on, future governments will have to maintain clarity about their determination to use prerogative power in a way which is legitimate, does not run counter to the constitution and does not pursue a political advantage. Though he may disagree with the outcome, this case has sent the strongest possible signal that the Prime Minister must respect his constitutional responsibilities.

Prof Theodore Konstadinides (University of Essex), Dr Noreen O’Meara (University of Surrey), and Riccardo Sallustio (Solicitor, Grimaldi SL LLP)

(Suggested citation: T. Konstadinides, N. O’Meara and R. Sallustio, ‘The UK Supreme Court’s Judgment in Miller/Cherry: Reflections on Its Context and Implications’, U.K. Const. L. Blog (2nd Oct. 2019) (available at