UK Supreme Court on Prorogation: The Role of Unwritten Constitutional Principles

This morning, the UK Supreme Court issued its unanimous decision on Prime Minister Boris Johnson’s advice to the Queen to prorogue Parliament. Its decision in R (on the application of Miller) v. The Prime Minister and Cherry and others v. Advocate General for Scotland held that the Prime Minister had broken the law because the length of the prorogation without reasonable justification “prevented Parliament from carrying out its constitutional role [of holding the Government to account]” [para.56].

The decision is significant in finding that considering whether the Prime Minister acted lawfully in this instance is justiciable and that the reasons for finding that he did not act lawfully lie in the principles underlying responsible government. Finding the length of the prorogation sufficient to address the matter, the Court did not consider whether Prime Minister Johnson’s motive was relevant, since that would have to be addressed only if the Prime Minister’s advice to the Queen was lawful [para. 54]. Furthermore, the Court declined to consider the Queen’s action in granting his request for prorogation; no one argued other than that her acceptance of his advice was required by constitutonal convention (para. 30].

The decision (of 11 judges) is a response to two appeals. One appeal was by the Prime Minister of a decision by the Scottish Court of Session that the prorogation was improper, both because of motive (and its related) length. The other appeal was from a decision of the Queen’s Bench Division of the High Court of Justice, which held that the Prime Minister’s request to prorogue Parliament was not justiciable.

The Order in Council ordering prorogation, after the Prime Minister requested that the Queen grant it, provided that it begin no earlier than September 9th and no later than September 12th and end October 14th.

The Court addressed the following four issues:

(1) Is the question of whether the Prime Minister’s advice to the Queen
was lawful justiciable in a court of law?
(2) If it is, by what standard is its lawfulness to be judged?
(3) By that standard, was it lawful?
(4) If it was not, what remedy should the court grant?

The arguments against the Court’s hearing these appeals were based on the following: that in giving advice to the Queen, the Prime Minister was accountable only to Parliament and “the courts should not enter the political arena but should respect the separation of powers” (para. 28].

The Court prefaced its consideration of this issue with the following remarks:

First, the power to order the prorogation of Parliament is a prerogative power: that is to say, a power recognised by the common law and exercised by the Crown, in this instance by the sovereign in person, acting on advice, in accordance with modern constitutional practice. It is not suggested in these appeals that Her Majesty was other than obliged by constitutional convention to accept that advice. In the circumstances, we express no view on that matter. That
situation does, however, place on the Prime Minister a constitutional responsibility, as the only person with power to do so, to have regard to all relevant interests, including the interests of Parliament. [para. 30]

Furthermore, “almost all important decisions made by the executive have a political hue to them. Nevertheless, the courts have exercised a supervisory jurisdiction over the decision of the executive for centuries. Many if not most of the constitutional cases in our legal history have been concerned with politics in that sense.” [para. 31]

As for the Prime Minister’s accountability to Parliament, this cannot occur if Parliament is prorogued. In any event, this does not foreclose a minister’s accountability to the courts. [para. 33] The Court’s final preliminary point is that “by ensuring that the Government does not use the power of prorogation unlawfully with the effect of preventing Parliament from carrying out its proper functions, the court will be giving effect to the separation of powers.” [para. 34]

In relation to prerogative powers, there are two issues: 1) whether a prerogative power exists and if so, its extent (all parties to the proceedings agree this is justiciable); and 2) if the power exists and has been exercised within its limits, is it open to legal review? That is,

[t]he question then is not whether the power exists, or whether a purported exercise of the power was beyond its legal limits, but whether its exercise within its legal limits is
challengeable in the courts on the basis of one or more of the recognised grounds of judicial review. [para. 35]

Prerogative powers are recognized by common law and must be compatible with common law principles: “In particular, 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.” [para. 38] The courts have “responsibility to determine the legal limits of the powers conferred on each branch of government, and to decide whether any exercise of power has transgressed those limits.” [para. 39]

The Court describes the constitutional principles developed by common law as “legal principles of the constitution”, including those “concerning the conduct of public bodies and the relationships between them”, which, in turn, include prerogative powers [para. 40].

One of the “fundamental principles” applying here is “parliamentary sovereignty” in the sense that “laws enacted by the Crown in Parliament are the supreme form of law in our legal system, with which everyone, including the Government, must comply ” [para. 41]. Therefore “[a]n unlimited power of prorogation would … be incompatible with the legal principle of Parliamentary sovereignty.” [para. 42] This does not mean that Parliament cannot be prorogued, even though it cannot exercise its authority during that period, as long as it is for a relatively short duration.

The other principle relevant here is “parliamentary accountability”, which refers to responsible government and the various ways in which ministers are answerable to Parliament [para. 46]. Parliamentary accountability is not undermined by short periods of prorogation, “[b]ut the longer that Parliament stands prorogued, the greater the risk that responsible government may be replaced by unaccountable government: the antithesis of the democratic model.” [para.48] The Court explains,

that a decision to prorogue Parliament (or to advise the monarch to prorogue Parliament) will be unlawful if the prorogation has the effect of frustrating or preventing, without reasonable justification, the ability of Parliament to carry out its constitutional functions as a
legislature and as the body responsible for the supervision of the executive. In such a situation, the court will intervene if the effect is sufficiently serious to justify such an exceptional course. [para. 50]

Applying this standard requires determination of whether the Prime Minister’s explanation is a reasonable justification for proroguing Parliament for this length of time. This assessment is feasible and thus within the court’s capacity to determine. The question of whether the Prime Minister’s advice to the Queen was lawful is justiciable, requiring the Court to determine the boundary between the exercise of the prerogative power and the principles of Parliamentary sovereignty and accountability. [para. 53]

The prorogation “prevented Parliament from carrying out its constitutional role for five out of a possible eight weeks between the end of the summmer recess and exit day on the 31st of October” [para.56]. Here the looming date of exit from the EU was crucial and Parliament, in particular the House of Commons, had a right to voice its opinion on it and the Government had a responsibility to face the House of Commons. [para. 57]

Acknowledging that the Government “must be accorded a great deal of latitude in making decisions of this nature”, the Court was concerned not with the Prime Minister’s motive but whether he needed to request a lengthy prorogation.

The Court had before it a Memorandum from the Director of Legislative Affairs to the Prime Minister and copied to others that indicated that “[t]his had been the longest session since records began”, there were few bills close to royal assent and time would be better spent on new measures, and it would be “‘extremely pressured'” to start the new session earlier than October 14th [para. 17]. But this does not explain why five weeks were necessary and it does not address the various matters that Parliament would have to address in relation to any new agreement with the EU or other activities in which Parliament would have to be involved in order to prepare for October 31st. The Prime Minister’s own comments on the Memorandum do not reflect his constitutional responsibility, rather than his role as leader of the Government and concern with its policies. [paras. 58-61]

The Court held the decision to request prorogation is therefore unlawful and null and of no effect [para. 69]. The next step is for Parliament, since it was never prorogued.

It remains an open question whether improper motive, such as avoiding scrutiny by the legislative body, may be a reason for finding a request to the Queen (or, in Canada, the Governor General) unlawful. However, the decision does give life to the notion that fundamental constitutional principles can provide the basis for finding government action improper. The extent to and circumstances under which this may be the case are worth further consideration. Nevertheless, it appears that they may have more significant status, that is, as legal principles, than as “principles of political philosophy”, as Miller J.A., of the Ontario Court of Appeal would have them in Toronto (City) v. Ontario (Attorney General), the subject of my next post.


  1. This has been fascinating stuff for lawyers and I’m not surprised by the result. All the signs were there last week that the Supreme Court was going to find against the PM and rightly so in my view. The fallout from this in the next few days is going to be just as gripping.

    Just an amusing personal postscript. Lady Hale was my Family Law tutor at university. I was in the first group she ever taught in her first job and I will always remember the withering look she gave me when I made a smart arse comment that a sperm donation without the wife’s knowledge might constitute adultery (which I had seen in a respected legal journal but passed off as my own original thought.) Served me right.

    By the way, no need to add this to any discussion unless you want to.