In the opening lines of Miller/Cherry, Lady Hale and Lord Reed, giving the unanimous judgment of the court, say that the case ‘arises in circumstances which have never arisen before and are unlikely to ever arise again.’ The case, they said, is a ‘one off.’ [1] One of the arguments raised by the Applicants in the recent Canadian Federal Court case of MacKinnon v Canada was that, while not legally binding, the analysis of the UKSC in Miller/Cherry should be applied to (then) Prime Minister Trudeau’s advice to the Governor General to prorogue the Canadian Parliament for 77 days. In other words, the case effectively asked, to what extent was Miller/Cherry really a ‘one off?’
In MacKinnon, Chief Justice Crampton concluded that he would approach the use of Miller/Cherry with ‘caution’ [169] concluding that the differences between the ‘legal frameworks and factual circumstances’ were such that ‘it would not be appropriate’ to adopt the UKSC analysis wholesale. However, Crampton CJ also found that the ‘Miller II decision was issued by a unanimous 11-member panel of a high reputed and influential Court’ and so he would ‘not hesitate to cite it where I consider it appropriate to do so.’ [169] The constitutional questions raised by the Applicants in placing these two cases in dialogue with each other are ‘novel’ [312] and ‘may well have future importance’ [313], Crampton CJ emphasised in finding that the Government of Canada should pay Applicants’ costs in this case.
This post has three parts. It first clarifies, for readers in the UK, the facts, circumstances, and findings of MacKinnon v Canada. Second, it identifies three areas where the analysis provided in MacKinnon raises useful questions, or places an interesting gloss, on arguments made in Miller/Cherry. Third and finally, the post considers the consequences of MacKinnon. MacKinnon begins with the observation that ‘Miller II appears to be the only case in the history of the Commonwealth where a court interfered with the exercise of the Crown prerogative to prorogue Parliament.’ [14] The post also draws on insightful analysis in Canada from Professors MacDonnell and Daly to clarify in what senses MacKinnon is and is not a ‘one-off’. Miller/Cherry will, Professor Poole argues, be discussed 200 years from now, and the impact of MacKinnon may well be similarly profound.
1. MacKinnon v Canada
On 6 January 2025, under pressure from his own party on how to respond to the threat of 25% tariffs from the United States [24-26], then Prime Minister Justin Trudeau announced the prorogation of the Canadian Parliament for five sitting weeks [291]. As in Miller/Cherry, the question of the length of the prorogation was disputed because of previously scheduled (or conventionally held) recesses [Miller/Cherry, 17]. The reasons for the Canadian prorogation were multiple, including the ‘paralysation’ of Parliament [41]. However, the effect of the prorogation was to give the governing Liberal party the time to run a leadership contest following the announcement of Trudeau’s resignation, which would eventually produce (current) Prime Minister Mark Carney. The Applicants were concerned citizens, granted public interest standing. Chief Justice Crampton in the Federal Court ultimately found that while the matter of prorogation itself was justiciable, Trudeau’s prorogation was lawful.
There are, of course, significant differences, between the legal and factual circumstances of the two cases. Two differences are particularly important, and Crampton CJ was right to treat Miller/Cherry with ‘caution’. First, an important legal difference is that Canada has a codified constitutional text. This means, as Crampton CJ said, that there is ‘more scope for the UKSC to draw upon unwritten constitutional principles than would be possible under the Canadian jurisprudence.’ [164] A second key difference identified by Chief Justice Crampton, this one factual, was that in Miller/Cherry ‘a fundamental change was due to take place in the Constitution of the United Kingdom.’ [Miller 57] and [MacKinnon 165]. While these significant differences must be kept in mind, the Applicants’ submissions in MacKinnon put the two cases directly in dialogue with each other. For that reason alone, it is helpful to consider them together.
2. Insights from MacKinnon for Miller/Cherry
Not only are there insights for MacKinnon to be drawn from Miller/Cherry, but there are also interesting questions raised for Miller/Cherry by MacKinnon. Acknowledging Kuo’s recent, excellent admonishment to take care when making comparisons in constitutional law, to remain focused on the ‘multiplicity of constitutions’ and not just their form, I think there at least four interesting insights to be found.
A. Conventions versus Prorogations
Very interestingly, the respondent Canadian Government sought to argue that prorogation was not an exercise of a prerogative power at all, but rather an exercise of a constitutional convention by the Prime Minister instead. [55] This was, I thought, an interesting and alternative argument to try to advance the non-justiciability point, which was not argued in the Miller/Cherry case. While it is clear that the exercise of prorogation is mediated by convention in United Kingdom, this is different from claiming that prorogation is a pure exercise of convention not prerogative power.
It was interesting as well that the Respondent, the Canadian government, attempted to distinguish Miller/Cherry by arguing that ‘in Canada, “many commentators take the view that the governor general has a discretion to refuse and certainly to ‘warn and encourage’ regarding a Prime Minister’s request to prorogue.”’ [66] While Crampton CJ was ultimately unsympathetic to these submissions, they nevertheless raise a hugely important question in UK constitutional law. The issue, as I have argued before, is about the relationship between political outcomes and legal consequences. The REFERENCE by the Lord Advocate on Devolution Issues is particularly significant here because it is a case where Lord Reed in UKSC held that, with respect to holding a non-binding independence referendum, ‘legal consequences may flow from political facts.’ [142]
B. Parliamentary Accountability
One of the principles advanced in Miller/Cherry was the principle of parliamentary accountability [Miller 46-47], which is less well-established in UK constitutional law than the related principle of parliamentary sovereignty. The development of parliamentary accountability, which Crampton CJ said ‘does not appear to have been recognised as a principle of the Canadian constitution’ [197] should be understood instead, he said, in terms of responsible government. ‘Responsible government’ Crampton CJ said, ‘consists of two basic elements: (1) the responsibility of individual ministers and their respective departments for their activities; and (2) the collective responsibility and accountability of the Executive to the legislative assembly, which includes the Prime Minister maintaining the confidence of the House of Commons.’ [198] This is, I think, an interesting way of unpacking the meaning of parliamentary accountability in the UK context as well. While responsible government is a constitutional convention in the UK, understanding parliamentary accountability as the legal face of responsible government helps delineate what the UKSC set out to protect in Miller/Cherry.
It is interesting and important as well that, in the Canadian context, Crampton CJ placed huge emphasis on responsible government, declaring it ‘most important non-federal characteristic of the Canadian constitution.’ [199] I think this argument for the existential importance of responsible government to parliamentary democracy helps explain why the UKSC considered themselves compelled to give the principle the legal face of parliamentary accountability in Miller/Cherry.
C. Reasons
In many ways, the reasoning of MacKinnon tracks the reasoning in Miller/Cherry, but not always. Miller/Cherry famously holds that:
It is impossible for us to conclude, on the evidence which has been put before us, that there was any reason – let alone a good reason – to advise Her Majesty to prorogue Parliament for five weeks, from 9th or 12th September until 14th October. We cannot speculate, in the absence of further evidence, upon what such reasons might have been. It follows that the decision was unlawful. [61]
The emphasis in MacKinnon is subtly, and interestingly, different. Crampton CJ concluded that ‘The Prime Minister was not obliged to give any reasons for proroguing Parliament. However, having done so, it was open to the Applicants to challenge them.’ [281] This analysis gets to the same place, but the phrasing is different. In MacKinnon, the absence of reasons raised the justificatory burden for the Respondent. This is, I think, what the UKSC was arguing, but layering MacKinnon on top of the Miller/Cherry analysis helpfully clarifies that there was no duty to provide reasons, but the absence of reasons raised the justificatory burden for the Prime Minister.
D. Role of Uncodified Constitutional Principles, Particularly Democracy
As discussed above, Crampton CJ is careful to argue that principles will play a different role in a codified constitution. Nevertheless, the use of constitutional principles in this case is instructive for reflecting on the way in which the principles of parliamentary sovereignty and accountability were employed in Miller/Cherry. It is particularly interesting that the Applicants in MacKinnon called upon an even higher constitutional principle of parliamentary democracy, arguing that ‘the principle of democracy infuses the principle of parliamentary sovereignty and the rule of law [189].’ The idea of a common law principle of democracy may help articulate the UKSC’s analysis in Miller/Cherry as well, and Professor Pal has very helpfully developed this idea in a Canadian context.
To demonstrate that constitutional principles could invalidate executive action in MacKinnon, the Applicants had to show that their arguments fell into one of the two categories where it has been recognised that constitutional principles may be used by courts: ‘(1) in the interpretation of constitutional provisions; (2) as structural doctrines to fill gaps or answer questions on which the written Constitution is silent: Toronto (City) at paras 55–56 [emphasis added].’ [218] In MacKinnon, Crampton CJ concluded that the Applicants had ‘failed to argue or demonstrate that the Constitution’s text and architecture necessarily imply that those unwritten constitutional principles set limits on the Prime Minister’s authority to advise the prorogation of Parliament in the ways they allege.’ [emphasis in original 227]
With respect to the Toronto (City) approach, I think the UKSC in Miller/Cherry takes itself to be using constitutional principles in both of the two Toronto (City) ways: as interpreting legal principles and as filling structural gaps. The difference is, of course, that the requirement of necessary implication was borne out Miller/Cherry. Indeed, I think this is exactly what the hypothetical of unlimited prorogation in Miller/Cherry was trying to show: the structure of the UK constitution necessarily implied that the principles of parliamentary sovereignty and accountability constrained the Prime Minister in such a way as made the prorogation unlawful.
The difference in finding that necessarily implication was borne out in Miller/Cherry, I think, was because Crampton CJ concluded that the nature of the constitutional change in MacKinnon was different. Professor MacDonnell persuasively argues that MacKinnon took the right approach on these facts, and that uncodified principles are often under determined because they should be held in reserve, and her analysis chimes with much of the analysis offered by Professor Endicott at the time of Cherry/Miller (albeit on a very different set of facts).
3. Further Issues
This post has explored only a few of the many very interesting issues arising from placing Miller/Cherry and MacKinnon in dialogue with each other. Two further issues are so significant they are worth briefly flagging.
Particularly important in Canada is the question, deftly handled by Professor Daly, about the appropriate standard of review for the existence of a prerogative power as opposed to its exercise; particularly post-Vavilov.
Very interesting as well, with respect to work Professors Lazarus and Khaitan have done on constitutional scholars as constitutional actors, is the role of existentially significant experts like Professor Peter Oliver in establishing the content of Constitutional Law. Professor Oliver submitted an expert report on behalf of the Respondent Canadian Government [43], which was admitted as expert evidence by the Court [44.] Interestingly, though, some passages from the Oliver report were specifically struck out as Crampton CJ found them to be ‘matters for the court to determine.’ [50.]
Despite some parts of the analysis being inadmissible, Crampton CJ’s analysis wove in and out of agreement with Professor Oliver’s, demonstrating the impact he had on the case. Similarly, in Miller I, analysis from Professors King, Hickman, and Barber, for instance, was cited to support the findings in the case. In this way, Mackinnon, like Miller I, is yet another example of a case where academics contributed to the project of determining the content of the law.
4. Conclusion
In the opening lines of Miller/Cherry, the UKSC says that the circumstances of the case are difficult, but that the law is used to ‘rising to such challenges.’ [1] MacKinnon demonstrates, I think, both the ways in which Miller/Cherry was a distinctive ‘one-off’ set of facts, and the ways in which it has permanently changed the law both in the United Kingdom, and across the Commonwealth. MacKinnon flags that Miller/Cherry has been favourably cited in New Zealand [161], and this is unlikely to be the last time these cases are in dialogue with each other.
Sincere thanks to Mike Gordon and Paul Scott at the UKCLA, as well as to Shreya Atrey, Achas Burin, and Hayley Hooper for very helpful comments on earlier drafts. The usual disclaimers apply.
Leah Trueblood is Fellow and Tutor in Public Law at Worcester College, Oxford
She blogs weekly at https://substack.com/@hardcasesmakegoodlaw
Suggested citation: L. Trueblood, ‘Judicial Review of Prorogation in Canada: The Applicability of Miller/Cherry v Prime Minister to MacKinnon v Canada’, U.K. Const. L. Blog (29th April 2025) (available at https://ukconstitutionallaw.org/))
