A good deal has been said in recent days about whether the Government’s advice to the Queen concerning the prorogation of Parliament raises a legal question on which courts can properly adjudicate. As is well-known, English and Scottish courts have so far differed sharply on this point: in the Cherry case, the Inner House of the Court of Session (according to the summary of its judgment that has so far been published) held that the issue was justiciable and that the Government’s advice (and the prorogation that flowed from it) was unlawful. In contrast, the Divisional Court in London emphatically held in Miller (No 2) that the matter was not justiciable.

My own view is that the Divisional Court’s stance on what should be regarded as non-justiciable is far too broad, and that the position it reaches does not withstand analysis. In particular, the Court places disproportionate emphasis on the fact that it cannot make abstract determinations of how long is too long when it comes to prorogation, while approaching the whole issue of justiciability in unnecessarily sweeping terms that pays insufficient regard to the more subtle approach that courts have adopted over the last 30 or so years following the House of Lords’ seminal judgment in GCHQ [1985] AC 374. The purpose of this post, however, is not to offer a detailed critique of the Divisional Court’s judgment. Rather, it is to set out (what seems to me to be) a straightforward argument: that treating the central issue raised by Cherry and Miller (No 2) as non-justiciable because it is “political” amounts to a strikingly unsophisticated approach that is both incompatible with the tenor of modern case law in this area and misconceives the nature of the legal question that falls for determination.

The central issue in Cherry and Miller (No 2) is whether the advice tendered by the UK Government to the Queen concerning the prorogation of Parliament for five weeks is lawful or unlawful. Prorogation is accomplished through the exercise of a legal power in the form of a prerogative power, and advice tendered to the Queen concerning its use amounts to an exercise by the Government of prerogative power ancillary to the prorogation power itself. It is well-established that the mere fact that a power falls under the prerogative rather than taking a statutory form does not in and of itself render it non-justiciable or otherwise immune from judicial review. The default position is therefore that the normal principles of judicial review apply to the exercise of any given prerogative power.

Once our starting-point is clearly established, other crucial matters follow. First, and importantly, is the widely recognised principle that no governmental legal power is unfettered. All legal powers held by the Government are legally finite, and their boundaries are determined, among other things, by reference to the purposes for which they may and may not legitimately be used. There is no good reason why this should not apply in the case of the prorogation power and the Government’s ancillary authority to advise the Queen as to its exercise. It follows that those powers are legally limited, among other things, by reference to the purposes for which they may and may not legitimately be used. What those purposes are is a legal question for determination by courts in the ordinary way.

When such questions arise in respect of statutory powers, they are resolved, first and foremost, by means of statutory construction: that is, the legislative text is examined and construed by the court, and the purposes for which the power can and cannot lawfully be used are thus determined. However, the process of statutory construction is rarely a purely literal one that entails recourse to nothing more than a dictionary, and it frequently involve the attribution of meaning to the statutory text by reference to broader relevant legal, including constitutional, principles. This approach is so well-established that authority need hardly be cited, but key examples — which illustrate the breadth of the approach — include Robinson v Secretary of State for Northern Ireland [2002] UKHL 32 (in which constitutional principles relating to the existence of functioning institutions of government significantly influenced the interpretation of the relevant legislation), R v Secretary of State for the Home Department, ex parte Simms [2000] AC 115 (in which constitutional principles concerning individual rights played a major part in the interpretive process) and R v Secretary of State for the Home Department, ex parte Fire Brigades Union [1995] AC 513 (in which the constitutional principle of the separation of powers assumed an axiomatic role).

In the case of prerogative powers, there is plainly no formal textual starting-point such as there is when statutory powers are in play. It follows that it may be more difficult to determine the boundaries of such powers, including by reference to the purposes for which they can and cannot lawfully be used. It does not, however, follow that no such boundaries exist. Nor does it follow that questions as to the location of such boundaries are anything other than legal questions. Moreover, just as fundamental constitutional principle may cast light on the proper meaning of statutory texts — and thus on questions as to the proper and improper use of statutory powers — so fundamental principle may illuminate and determine the boundaries of prerogative power, including the purposes to which they can and cannot lawfully be put.

It is in precisely this way that the foundational principles underpinning the UK’s uncodified constitution infuse and shape the legal framework — whether, for relevant purposes, that framework is formed by statutory or prerogative powers — within which Government is required to operate. Indeed, to overlook this point is to commit a constitutional solecism, for it draws an unwarrantedly sharp distinction between constitutional principle and constitutional law. The principle of legality, if it is understood as a principle of statutory construction, captures this point — by enable constitutional principle to shape the interpretation of legislation — but only incompletely. Properly appreciated, the principle of legality is one that enables — and requires — the legal-constitutional framework to be understood by reference to and in the light of fundamental principle, whether the relevant aspect of that framework takes statutory or some other form. (By seeking to confine the principle of legality to the interpretation of legislation, on the ground that it is merely a principle of statutory construction, the Divisional Court in R (El Gizouli) v Secretary of State for the Home Department [2019] EWHC 60 (Admin) fell into error — an error which the Supreme Court ought to correct when it decides Cherry/Miller (No 2).)

In the Cherry and Miller (No 2) cases, the question is therefore whether the use to which the prorogation power has been put results in the boundaries of the power having been exceeded, with reference to any purposes for which the power may not lawfully be exercised. The Divisional Court in Miller (No 2) rightly notes that there are several purposes for which the power can lawfully be exercised. But the question here is whether the power has been used for a purpose for which it cannot be so exercised. This raises issues both of evidence and legal principle. The evidentiary question is whether the true reason for prorogation was — to use the language adopted by the Inner House of the Court of Session — to “stymie” parliamentary scrutiny of the Executive. I take no position in this post on that question, save by way of noting that the Court of Session considered the answer to that question to be “yes”. Two legal questions then arise. Is the stymying of Parliament in this way a purpose for which the prorogation power can lawfully be exercised? And is dealing with this matter something that a court can legitimate do, or are the issues that arise non-justiciable?

Notwithstanding all of the sound and fury in the surrounding political context, neither of these questions, it seems to me, raise especially controversial or difficult legal or constitutional issues. The first question — whether the stymying of parliamentary scrutiny of the Executive forms one of the purposes to which the power can lawfully be put — falls to be answered by reference to fundamental constitutional principle. As Jake Rowbottom has noted, one such principle is the representative nature of democracy in the UK and institutional arrangements, including Executive accountability to Parliament, that are thereby necessitated. Recourse to such principle in determining the limits of the prorogation power should hardly be a controversial step. Nor should the conclusion that it is incompatible with the nature of parliamentary democracy in the UK for the Executive to have a legally unfettered power to suspend the operation of Parliament for the purpose of shielding the Executive from parliamentary scrutiny.

That leads on to the question whether, notwithstanding all of the foregoing, the issues are non-justiciable. The answer to that question — an answer that largely follows from the foregoing analysis — is surely “no”. This is so because of what, once the issues are clearly understood, the court does not need to do in order to answer the relevant legal question. Paul Craig has correctly pointed out that it is misconceived to suppose that the exercise of the prorogation power necessarily involves matters of “high policy”, noting that its exercise is almost always mundane. Indeed, it is possible to go even further in the present context, by arguing that the issue at stake in Cherry and Miller (No 2) is justiciable because it does not, in the first place, raise any question for judicial determination upon which an argument of non-justiciability could bite.

Such questions could, at least in theory, arise if (for example) a court were asked to rule on whether three days or five days would be a reasonable, and so lawful, duration for a period of prorogation. This would raise precisely the sort of problem referred to by the Divisional Court in Miller (No 2) when it referred to the “insuperable difficulty that it is impossible for the court to make a legal assessment of whether the duration of the prorogation was excessive by reference to any measure”. Crucially, however, no such issue actually arises in the Miller (No 2) and Cherry cases. For one thing, there is no need for the court — contrary to the view that the Divisional Court took — to determine whether the duration was excessive. (This is not, however, to deny that inferences may properly be drawn from the duration of a period of prorogation when a court is determining, in evidentiary terms, what the true purpose was. Moreover, in the instant case, the purpose advanced for the prorogation is that the Government wants to open a new session of Parliament and hold a Queen’s Speech. This signally fails to explain why such an abnormally long period of prorogation has been chosen, and thus gives rise to an inference that an improper purpose is at work.)

Thus, far from requiring the Court to determine whether the duration is excessive, the issue in Cherry and Miller (No 2) requires the court only to determine whether, to begin with, prorogation was undertaken for a purpose that was legally impermissible because it lies outside the range of purposes for which the power can lawfully be deployed. This is a crisp question of constitutional law concerning the scope of the discretionary power to prorogue, as distinct from a question about whether discretion has been lawfully exercised. Such a question of law, about the scope of the Executive’s legal powers, is manifestly one that lies within the field of matters with which courts can properly deal.

The result is that to approach Cherry and Miller (No 2) in terms of whether the courts can stretch the bounds of justiciability in a way that facilitates judicial scrutiny of the exercise of the prorogation prerogative is misconceived. It is misconceived because the legal issue at stake is not one upon which the non-justiciability doctrine can properly bite. That doctrine is concerned with limiting judicial involvement in the evaluation of the exercise of governmental powers whose use is capable of giving rise to questions that are unsuited, under the separation of powers, to analysis by courts on legal grounds. The justiciability doctrine is, however, logically incapable of biting upon questions about whether a given power exists and, if so, what its legal boundaries are. Questions about the purposes for which legal powers can and cannot lawfully be used are legal questions about the scope of such powers. It is questions of precisely that nature which are raised by the Miller (No 2) and Cherry cases. Consequently, the non-justiciability doctrine has no relevant application — and the suggestion by the Divisional Court that the “political” nature of the issue shields it from judicial review is entirely wide of the mark. Whether the Supreme Court will be prepared to treat the matters before it as justiciable remains to be seen, but there is no good legal reason for treating them as non-justiciable.

I am grateful to John Bell, Paul Craig, Philip Murray and Jack Williams for discussion of matters raised in this post and/or for comments on an earlier draft. The usual disclaimer applies.