Hasan Dindjer: Prorogation as a Breach of Parliamentary Sovereignty

Does proroguing Parliament under the present circumstances breach the principle of parliamentary sovereignty? The Divisional Court in Miller v Prime Minister (‘Miller (No 2)’) thought not. It held that the principle is not wide enough to be threatened by prorogation ([63]-[64]). I argue here that this conclusion rests on too narrow a view of parliamentary sovereignty. That principle, I propose, is best understood to include—or imply—the proposition that Parliament must have meaningful opportunities to legislate on matters of vital public importance. A prorogation which denies it such opportunities, absent sufficient justification, is an unlawful breach of parliamentary sovereignty. Although I do not consider the Prime Minister’s reasons for prorogation in the present case (and hence not the decision’s overall lawfulness), I suggest he faces a heavy burden of justification.

Two views of parliamentary sovereignty

In Miller (No 2), the Prime Minister advanced ([59]), and the Divisional Court apparently endorsed ([62]-[64]), what we might call the narrow view of parliamentary sovereignty. Its two main, Diceyan principles (with immaterial caveats omitted) are:

Plenary Authority: Parliament may legislate on any subject-matter and may enact into law any content whatever.

Legal Supremacy: Laws duly enacted by Parliament are binding on all within the jurisdiction and override any contrary legal norms (including those previously enacted by Parliament).

The first principle concerns the breadth of Parliament’s legislative power, while the second concerns the legal effects of its exercise. Neither, on the narrow view, has to do with the conditions under which Parliament must be able to exercise its powers.

In contrast, what I shall call the broad view understands parliamentary sovereignty to include (or imply) a further aspect:

Meaningful Legislative Opportunities: Parliament is sovereign only if it has meaningful opportunities to exercise its legislative powers. Denying it such opportunities without sufficient justification is a breach of parliamentary sovereignty.

Something of the spirit of the broad view is perhaps detectable in the Bill of Rights’ requirement that ‘Parliaments ought to be held frequently’—but this is extremely undemanding by modern standards: as Blackstone records (Commentaries, Vol 1, 149), the Meeting of Parliament Act 1694 specified that every three years was frequent enough.

The argument for the broad view is not historical. Instead, it seeks to understand the basis and implications of the modern legal principle of Parliament’s supreme, plenary authority, as it exists now in the constitutional democracy of the United Kingdom.

Legal powers and the conditions for their exercise

The argument proceeds from the nature of Parliament’s plenary legislative authority. Parliamentary sovereignty protects a power—a power of Parliament to enact law as it sees fit on any subject. But the law does not in any true sense protect a power unless it also protects the conditions for its meaningful exercise.

The courts are familiar with the idea that rights and principles of constitutional law must not simply be honoured formally but be made meaningful in fact. That is the standard approach to the interpretation and application of fundamental rights, both in domestic law and under the ECHR (see e.g. UNISON at [109]). Similarly, the law regulating prerogative powers ensures that statutes remain in ‘effectual operation’, rather than being made ‘redundant’ or ‘useless’ (Miller (No 1), [51]). There is no reason why the same approach should not apply to rules of structural constitutional law. A legal power that is fundamental to the constitutional order must be interpreted so as to be meaningful and effective.

Parliament’s plenary power to legislate implies, therefore, legal protection for the conditions that are necessary for it meaningfully to be exercised. The central such condition is that Parliament be permitted to sit for long enough and at such times as to address matters of substantial national importance. Typical, short, prorogations are unproblematic. But if Parliament stands prorogued at length while major issues cannot be addressed, and time is of the essence, it is denied meaningful opportunities to exercise its plenary legislative power. Though this meaningful opportunities principle does not necessarily constitute an absolute prohibition on such prorogations, it must at least require that they be supported by compelling reasons. I return to the principle’s application below.

It might be countered that the principle of plenary authority contains an implicit proviso, applying only when Parliament is sitting, so that prorogation does not affect Parliament’s plenary authority properly understood. Yet this interpretation, first, implies constitutionally outlandish results and, second, is incompatible with the normative basis on which the parliamentary sovereignty principle is endorsed by the courts.

To illustrate the first point, consider some more extreme possible cases of prorogation, as where the government advises that Parliament be prorogued:

(A) for many months to head off the possibility of embarrassing defeats as it tries to negotiate a complex treaty;

(B) because it fears defeat on a particular bill that is being debated and seeks to stop its passage through Parliament by a certain date;

(C) for several months, out of a sincere wish to devote its scarce resources to governing the country.

The Divisional Court’s aversion to ‘extreme hypothetical examples’ ([66]) notwithstanding, such examples are, in fact, revealing. For they describe what any plausible account of constitutional law must treat as unlawful uses of prerogative power. Such prorogations would reverse the constitutional settlement by nullifying Parliament’s supremacy over the executive and its ability to legislate. Quite apart from any improper purpose—which is probably not present in the hypothetical scenario (C)—prorogations like these would be unlawful precisely because they would make it impossible for Parliament to legislate as it saw fit for substantial periods of time. That is, such prorogations would breach the principle of plenary authority. It follows that that principle is not confined to circumstances where Parliament is already sitting; it applies generally. That explains why excessively long prorogations threaten Parliament’s sovereignty—and that may be so even when a prorogation is not as egregious as in these examples.

This conclusion is supported from another direction. The normative basis for the courts’ treating Parliament as sovereign is the value of democracy. In British Railways Board v Pickin, for example, Lord Simon noted that the ‘system by which…those liable to be affected by general political decisions have some control over the decision-making is parliamentary democracy’, whose ‘peculiar feature in constitutional law’ was ‘the sovereignty of Parliament’ (798E-G). Or, as Lord Hope put it in Jackson (at [126]) parliamentary sovereignty is ‘built upon the assumption that Parliament represents the people whom it exists to serve.’

As with any other principle of constitutional law, the legal rationale for parliamentary sovereignty bears on its proper interpretation. That parliamentary sovereignty is taken—surely correctly—to realise the value of parliamentary democracy tells strongly against any reading of the plenary authority principle which makes parliamentary sovereignty an irrelevance whenever Parliament is prorogued. For Parliament to fulfil its democratic function in a fast-moving world, it must be able to legislate and therefore to sit without being suspended for long periods. It is not enough that it be able to legislate while sitting, if its ability to sit is itself curtailed. If the concept of parliamentary sovereignty is to embody its democratic rationale, then, it must protect sufficient opportunities to sit and legislate on questions of vital public importance.

A legal requirement

If this understanding of parliamentary sovereignty is right, is there a further problem of establishing a ground of judicial review which might apply to an unduly long prorogation? I do not think so. After all, parliamentary sovereignty is a legal rule of the constitution, and the argument here is that one aspect of it must be a prohibition on certain unduly long prorogations. If, alternatively, one understood this prohibition as free-standing (rather than as an aspect of parliamentary sovereignty) that would make it no different from other rules of constitutional law which directly prohibit the use of the prerogative in certain ways, such as to frustrate Acts of Parliament.

One might also understand the relevant ground as breach of constitutional principle. It is well established that breaching a common law right can be unlawful—a matter sometimes treated by the courts as a distinct ground and sometimes as an aspect of reasonableness review, in appropriately heightened form as context demands (see e.g. Kennedy [51]-[54]). It should make no difference whether what is at stake is a fundamental right held by an individual or a fundamental duty of constitutional law which happens to be owed to the public at large (not least given the inter-connection of these two types of norm (see UNISON at [66]-[70])).  Understood as the potential breach of a constitutional principle, prorogation would be—as the claimants argued before the Divisional Court—‘unlawful unless it can be justified as reasonably necessary to meet a legitimate objective’ (UNISON, [89]).

Robust scrutiny

However precisely the legal complaint is categorised and the test formulated, judicial review of a long prorogation ought to attract robust judicial scrutiny. The Divisional Court disagreed, on the ground that the challenged prorogation was political and involved high policy [60]. Paul Craig and Mark Elliott have persuasively addressed this issue in the context of the court’s approach to justiciability. I add the following points concerning the intensiveness of substantive review.

First, the starting point should be that there is an alleged breach of a foundational constitutional rule, which should attract searching scrutiny just as where what is alleged is the breach of a fundamental right. Second, although the courts often defer to the executive on high policy decisions, courts also properly defer to Parliament and strive to protect and give effect to its legislative authority as far as possible. The political nature of the issue should not, therefore, redound to the benefit of the Prime Minister as against Parliament. Third, the very features that make prorogation political are also in part those which make it constitutionally suspect. What could be more political than what the claimants allege—undermining the democratic process by suspending the legislature? The problem is that constitutional subversion, deliberate or otherwise, is high policy par excellence—and yet its (arguable) presence calls for judicial vigilance, not acquiescence. Fourth, proroguing Parliament makes the normal channels of political constitutionalism largely defunct. As the Inner House effectively acknowledged in Cherry ([106]), this makes the case for legal intervention stronger (or the case against it weaker).

Finally, asking how long is plausibly required to prepare for a Queen’s Speech does not, in fact, involve a uniquely inappropriate form of judicial scrutiny. Whether a decision is required to further a policy agenda, given its costs and the available alternative, is just the sort of question that is the mainstay of judicial review. More generally, courts frequently decide whether a length of time is excessive, given the legal and constitutional principles at stake—for example, whether a criminal sentence was too long, whether a decision-maker gave an affected person sufficient notice, or enough time to respond to a consultation. Reasoned judicial decision is not precluded in such cases simply because no legal rule prescribes ex ante a perfectly precise cut-off.


What parliamentary sovereignty demands by way of meaningful opportunities to legislate is naturally context-dependent. The present context could hardly be more urgent. Parliament faces an issue of momentous national significance, with a new Prime Minister pursuing a new policy that has not been tested in a general election. Although Parliament will have a chance to vote before the 31st of October, it will be shut out of the process as it unfolds in most of the intervening period. That process may have many unpredicted twists and turns. It is impossible now to judge whether there might be changes in the position of the EU27 or of particular Member States, or in the actions or stated intentions of the Prime Minister. Parliament might in this period have found it necessary to react rapidly to this dynamic situation—perhaps in ways that would decisively shape the course of negotiations and therefore any possible deal or extension. By the time it returns from prorogation, a full month later, these opportunities may have passed. The Divisional Court’s observation (at [57]) that Parliament can act swiftly when needed does not answer the point. Parliament stands to be denied the opportunity to act at all when it might matter most.

I am grateful to Timothy Endicott for his comments on an earlier draft.

Hasan Dindjer, Examination Fellow, All Souls College, University of Oxford

(Suggested citation: H. Dindjer, ‘Prorogation as a Breach of Parliamentary Sovereignty’, U.K. Const. L. Blog (16th Sept. 2019) (available at https://ukconstitutionallaw.org/))