Supreme Court rules unanimously that the prorogation of Parliament was unlawful

24 September 2019 by

R (Miller) v The Prime Minister; Cherry and others v Advocate General for Scotland [2019] UKSC 41

In a historic decision, a panel of 11 justices of the Supreme Court has held that the decision of the Prime Minister, Boris Johnson, to prorogue Parliament for 5 weeks from 9 September to 14 October 2019 was unlawful on the basis that it constituted an unjustified frustration of the constitutional principles of Parliamentary sovereignty and accountability.

Giving the summary of the Court’s reasons for the decision, the President of the Supreme Court, Lady Hale, said that

when the Royal Commissioners walked into the House of Lords it was as if they walked in with a blank sheet of paper … Parliament has not been prorogued.

It follows, said Lady Hale, that the Speaker of the House of Commons and the Lord Speaker of the House of Lords “can take immediate steps to enable each House to meet as soon as possible”.


Although not directly about Brexit, it is very unlikely that this case would have come to court had it not been for the result of the referendum in June 2016 in which 52% of voters voted in favour of bringing the UK’s membership of the EU to an end after over 4 decades.

Following that vote there has been paralysis. Although Parliament voted to begin the process of exiting the EU by triggering Article 50 of the Treaty on the Functioning of the European Union (after the Supreme Court ruled that the Government could not do this without Parliament) and enacting legislation to repeal the European Communities Act 1972, there has been no agreement about what should happen next.

A number of political fault lines have opened up. Brexit hardliners argue that to give proper effect to the result of the referendum, the UK has to be free to set its own immigration policy and strike its own independent trade deals with other countries. Some argue that if the EU will not agree to an exit deal that would allow this, Britain should leave without a deal.

Remain hardliners argue that a second referendum is needed, contending that the result of the 2016 referendum is unsafe on the basis that politicians on the Leave side were not honest with the public and/or that the difficulties that would arise from leaving have become so much clearer that it would be right for the public to be asked the question again.

Then there are those in the middle, who accept that Britain should leave the EU in accordance with the result of the vote, but believe that it is important that Britain agree a negotiated exit to prevent the risk of the significant consequences for the economy and for peace in Northern Ireland that could result from leaving without a deal. But even then there is no clear agreement about the exact nature of this negotiated relationship — e.g. whether the UK should remain within the EU Customs Union and/or the Single Market.

The previous Prime Minister, Theresa May, negotiated a deal with the EU to seek to ensure a smooth transition that would leave many of the major questions for the future. But to take effect it required the approval of Parliament. However, it was rejected three times by the House of Commons between January and March 2019. After failing to get her policy through, Mrs May announced her resignation in May 2019.

On 24th July 2019 Boris Johnson replaced her as Prime Minister. As one of the politicians who had campaigned for Brexit, he aligned himself with the hardcore tendency and pledged that he would break the deadlock by ensuring that Britain would leave the European Union by 31st October 2019, with or without a deal.

The difficulty was that Parliament stood in his way. On 14th March 2019 the Commons had voted (by 312 to 308) to reject a no-deal Brexit under any circumstances. At Parliament’s behest, two extensions to the exit deadline were then agreed, and in late summer 2019 it seemed likely that Parliament would pass further legislation to compel the Prime Minister to seek a further extension if he could not secure the agreement to a deal before that time (an Act to this effect, the European Union (Withdrawal) (No 2) Act 2019, also known as the ‘Benn Act’, would duly be passed just before the prorogation).

So the state of play on 28th August 2019 was that the Prime Minister wished to pursue a policy which embraced the possibility of leaving the EU without a deal, but Parliament seemed very likely to take legislative steps to prevent this.

That day, the Prime Minister advised the Queen to prorogue Parliament for 5 weeks from a date between 9th and 12th September until 14th October 2019. The prorogation then took place on 9th September 2019.

What is prorogation?

Parliamentary sittings are normally divided into sessions, usually lasting for about a year, but sometimes less and sometimes (as with the current session) much longer. Prorogation brings the session to an end. The next session begins, usually a short time later, with the Queen’s Speech where the Government sets out its legislative programme.

While Parliament is prorogued, neither House can meet, debate or pass legislation. Nor may members of either House debate Government policy, ask written or oral questions of Ministers or meet and take evidence in committees. In general, Bills which have not yet completed all their stages are lost and will have to start again from scratch in the next session of Parliament.

Meanwhile, the Government remains in office and can exercise its powers to make delegated legislation and bring it into force. It may also exercise all the other powers within existing law.

Importantly, prorogation is not the same thing as dissolution. Dissolution brings the current Parliament to an end and leads to a general election. Prorogation does not.

The power to prorogue is part of the royal prerogative. Unlike powers conferred by Act of Parliament, prerogative powers were historically exercised by the sovereign (i.e. the monarch) as personal powers. In modern times these are exercised by the Government of the day. To prorogue Parliament, therefore, the Prime Minister only needs to advise the sovereign accordingly. This advice is always followed — as it was in this case.

The legal challenge

Legal challenges were brought against this prorogation in each jurisdiction of the UK. As we explained here on the Blog, whilst the challenge in England & Wales was dismissed, the challenge in Scotland was upheld. The cases all went up to the Supreme Court.

The issues were as follows:

  1. Is the question of whether the Prime Minister’s advice to the Queen was lawful a matter which is justiciable (i.e. capable of review by the courts)?
  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 Government argued that the court should decline to consider the challenges, as they involved essentially political matters for which the Prime Minister was accountable only to Parliament. In deciding the lawfulness of the prorogation, the courts would be stepping impermissibly into the political arena.

The Court began its consideration of this by stating that the fact that the decision to prorogue was, in effect, a personal decision exercisable by the Prime Minister alone, meant that he was under

a constitutional responsibility, as the only person with power to do so, to have regard to all relevant interests, including the interests of Parliament. [30]

The Court then noted that the historic background demonstrated that “although the courts cannot decide political questions, the fact that a legal dispute concerns the conduct of politicians, or arises from a matter of political controversy, has never been sufficient reason for the courts to refuse to consider it” [31].

It then held that the fact that the Prime Minister remains accountable to Parliament is no answer to this. The reasons were first because the effect of prorogation is to prevent the operation of ministerial accountability to Parliament. Therefore, if Parliament were to be prorogued with immediate effect, there would be no possibility of the Prime Minister’s being held accountable until after a new session had commenced, which might mean that “the most that Parliament could do would amount to closing the stable door after the horse had bolted” [33].

Moreover, the courts have a duty to give effect to the law. The fact that the minister is politically accountable does not mean that he is therefore immune from legal accountability [33].

The Court then affirmed that if the issue was held to be justiciable, deciding it would not offend against the separation of powers. Rather, the court would be performing its proper function under the constitution 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 [34].

The Court then drew a crucial distinction between: (1) cases concerned with whether a prerogative power exists, and if it does exist, its extent; and (2) cases where it was accepted that a prerogative power exists and has been exercised within its limits, but the exercise of the power is sought to be challenged on some other basis.

All sides agreed that cases in type (1) would undoubtedly be justiciable. But the question of whether cases in type (2) would justiciable would depend on “the nature and subject matter of the particular prerogative power being exercised” (for authority for both principles, see Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374) [35].

Therefore, a key question was whether this case fell into type (1) or type (2). This issue — the question of whether the court was being required to determine where a legal limit lies in relation to the power to prorogue Parliament, and whether the Prime Minister’s advice trespassed beyond that limit — was noted to be closely related to the second issue in the case: the identification of the standard by reference to which the lawfulness of the Prime Minister’s advice is to be judged [37].

In essence, then, it seems that the Court considered that to make a determination on justiciability it would be assisted by an examination of whether there was a proper standard for the lawfulness of the exercise of the power. If so, the Court would be engaged in determining the legal limit of the power and therefore the matter would be justiciable as a type (1) case.

To draw a wider principle, I would suggest that it follows that this case affirms that where the existence of applicable legal standards to judge the exercise of a prerogative power is in question, it will be an important touchstone for justiciability if such standards are able to be identified.

This also raises a question of whether a claimant in a future case concerning a different prerogative power could seek to sidestep the issue of justiciability by disputing the boundaries of the power in question and inviting the court to adjudicate upon them. It may be argued in response that in an impermissible (non-justiciable) case, a court will not be able properly to identify relevant legal standards. For now, this remains unclear. The effect of this case on the wider doctrine of justiciability is therefore likely to be an issue for another day.

By what standard is the lawfulness of the advice to be judged?

The Court noted that whilst in principle it is relatively straightforward to determine the limits of a statutory power (since the power is defined by the text of the statute), determining the limits of a prerogative power is more complicated, as the power is not constituted by any document.

However, the Court affirmed that although it is not codified in a single document, the UK “nevertheless possesses a Constitution, established over the course of our history by common law, statutes, conventions and practice”. The boundaries of a prerogative power would be determined by these fundamental principles [38-39]. In essence, therefore, a prerogative power could not lawfully be used in contravention of a principle of constitutional law.

This case engaged two constitutional principles. The first is the principle of Parliamentary sovereignty: 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.

However, Parliamentary sovereignty is not confined merely to recognising the status of its legislation:

Time and again, in a series of cases since the 17th century, the courts have protected Parliamentary sovereignty from threats posed to it by the use of prerogative powers, and in doing so have demonstrated that prerogative powers are limited by the principle of Parliamentary sovereignty. [41]

For example, in the Case of Proclamations in 1611 the court protected Parliamentary sovereignty by holding that James I could not use prerogative powers to alter the law of the land and in Attorney General v De Keyser’s Royal Hotel Ltd [1920] AC 508 and again in R v Secretary of State for the Home Department, Ex parte Fire Brigades Union [1995] 2 AC 513 the courts prevented the Government from using prerogative powers to bypass Parliamentary statutes [41].

The Court held that Parliamentary sovereignty was engaged in the circumstances of this case:

The sovereignty of Parliament would, however, be undermined as the foundational principle of our constitution if the executive could, through the use of the prerogative, prevent Parliament from exercising its legislative authority for as long as it pleased. That, however, would be the position if there was no legal limit upon the power to prorogue Parliament (subject to a few exceptional circumstances in which, under statute, Parliament can meet while it stands prorogued). An unlimited power of prorogation would therefore be incompatible with the legal principle of Parliamentary sovereignty. [42]

It was no answer for the Government to say that this assessment involved engagement with potential extreme scenarios which need not be countenanced. If this claim was not justiciable, that would mean that there would be no circumstances whatsoever in which a court would be entitled to review a decision that Parliament should be prorogued. Therefore, the Court had to consider the implications of this [43].

In drawing this conclusion, the Supreme Court clearly departed from the Divisional Court, which had expressly refused to entertain extreme hypotheticals (see [66] of the Divisional Court’s decision here).

This was an important conclusion — in the words of the Court:

It must therefore follow, as a concomitant of Parliamentary sovereignty, that the power to prorogue cannot be unlimited. [44]

The second constitutional principle engaged was that of Parliamentary accountability:

Ministers are accountable to Parliament through such mechanisms as their duty to answer Parliamentary questions and to appear before Parliamentary committees, and through Parliamentary scrutiny of the delegated legislation which ministers make. By these means, the policies of the executive are subjected to consideration by the representatives of the electorate, the executive is required to report, explain and defend its actions, and citizens are protected from the arbitrary exercise of executive power. [46]

Whilst neither of these two constitutional principles would be placed into danger by a customary short prorogation, they would be jeopardised by an unlimited power to prorogue.

The key question therefore was how the legal limit on the power to prorogue should be defined so as to make it compatible with the principles of Parliamentary sovereignty and accountability [45; 48].

To address this question, the Court drew an analogy with the legal constraints on the exercise of a statutory power. In that sort of case, a measure taken under a statute which impedes or frustrates the operation of a relevant statutory principle must have a reasonable justification to be lawful (see R (UNISON) v Lord Chancellor [2017] UKSC 51).

Whilst the exercise of evaluating the lawful exercise of a prerogative power would differ, as the limits of a prerogative power cannot be derived from a process of statutory interpretation, the Court held that the governing principle would be similar. The exercise of the prerogative power would be limited by any constitutional principles with which it would otherwise conflict [49].

On this basis, the Court held 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. [50]

Conclusion on justiciability

The fact that there were standards by which the Court could judge the lawfulness of the exercise of this power yielded the answer to the issue of justiciability. In this case, the Court would be determining the limits of a prerogative power, rather than determining its exercise within its limits. The Court’s task would be “marking the boundary between the prerogative on the one hand and the operation of the constitutional principles of the sovereignty of Parliament and responsible government on the other hand”. This was a justiciable question [52].

Was the advice lawful?

The Court began its answer to this question with a ringing statement of constitutional principle:

We live in a representative democracy. The House of Commons exists because the people have elected its members. The Government is not directly elected by the people (unlike the position in some other democracies). The Government exists because it has the confidence of the House of Commons. It has no democratic legitimacy other than that. This means that it is accountable to the House of Commons – and indeed to the House of Lords – for its actions, remembering always that the actual task of governing is for the executive and not for Parliament or the courts. [55]

Therefore, the first question was whether the Prime Minister’s action had the effect of frustrating or preventing the constitutional role of Parliament in holding the Government to account. The answer:

of course it did. [56]

This was because this was not a normal prorogation in the run-up to a Queen’s Speech. Rather, it prevented Parliament from carrying out its constitutional role for 5 out of a possible 8 weeks between the end of the summer recess and exit day on the 31st October. It also prevented Parliament from having the opportunity to curtail the normal recess for the conference season, “given the extraordinary situation in which the United Kingdom finds itself” [56].

The particular circumstances of this case were critical:

A fundamental change was due to take place in the Constitution of the United Kingdom on 31st October 2019. Whether or not this is a good thing is not for this or any other court to judge. The people have decided that. But that Parliament, and in particular the House of Commons as the democratically elected representatives of the people, has a right to have a voice in how that change comes about is indisputable. And the House of Commons has 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 the critical issue for his Government at this time and that it is especially important that he be ready to face the House of Commons. [57]

Turning to the question of whether there was a reasonable justification for this prorogation, the Court noted that “the Government must be accorded a great deal of latitude in making decisions of this nature”. The Court then stated that it would not examine the Prime Minister’s motive for the prorogation, but rather “whether there was a reason for him to do it” [58].

According to the unchallenged evidence of former Prime Minister, John Major, the need to prepare a Queen’s Speech would normally lead to a prorogation of 4 to 6 days. The Court examined the documents provided by the Government to justify the prorogation in this case (which did not include a signed statement from the Prime Minister) and found that there was no proper explanation for why such an exceptionally long prorogation was needed [58-59].

The Court concluded as follows:

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 legal consequences of a declaration that advice given to the Queen was unlawful then had to be clarified. As the Court stated,

The essential question is: is Parliament prorogued or is it not? [62]

The Government argued that the Court had no power to declare the prorogation null and of no effect, because the prorogation itself was “a proceeding in Parliament” which cannot be impugned or questioned in any court by operation of article 9 of the Bill of Rights of 1688 (in England & Wales) and the equivalent provision of Claim of Right 1689 (in Scotland), which guarantee freedom of speech and debate in Parliament.

However, the Court held that whilst the prorogation itself takes place in the House of Lords and in the presence of Members of both Houses,

it cannot sensibly be described as a “proceeding in Parliament”. It is not a decision of either House of Parliament. Quite the contrary: it is something which is imposed upon them from outside. It is not something upon which the Members of Parliament can speak or vote. The Commissioners are not acting in their capacity as members of the House of Lords but in their capacity as Royal Commissioners carrying out the Queen’s bidding. They have no freedom of speech. This is not the core or essential business of Parliament. Quite the contrary: it brings that core or essential business of Parliament to an end. [68]

The Court then stated that the advice that led to the prorogation was unlawful as it was outside the powers of the Prime Minister to give it. This meant according to ordinary principles that it was null and of no effect. The Order in Council to which it led was likewise unlawful, null and of no effect and should be quashed. Therefore, the actual prorogation

was as if the Commissioners had walked into Parliament with a blank piece of paper. It too was unlawful, null and of no effect. [69]

This meant that Parliament has not been prorogued. As such,

Unless there is some Parliamentary rule to the contrary of which we are unaware, the Speaker of the House of Commons and the Lord Speaker can take immediate steps to enable each House to meet as soon as possible to decide upon a way forward. That would, of course, be a proceeding in Parliament which could not be called in question in this or any other court. [70]


This is a decision of monumental significance. As well as the huge political ramifications which are likely to follow, in a wider sense the decision sees a strong affirmation that the actions of the executive may be unlawful if they interfere with constitutional principles. The comments by former Supreme Court Justice, Lord Sumption, that this case would be unlikely to succeed because the issues would be likely to involve non-legally binding political conventions proved incorrect. The constitutional principles of Parliamentary sovereignty and accountability do have legal teeth.

Secondly, although the Justices did not actually use the formula offered by Lord Pannick QC in his submissions, this decision in effect clarifies that in constitutional terms it is Parliament that is the senior partner and the Government that is the junior. The Government will not be permitted to exercise its powers to frustrate Parliamentary sovereignty or accountability without proper justification.

But it is also important to note what the Court did not decide. Unlike the Scottish Inner House, the Supreme Court — perhaps conscious of the sensitivity of this case — came to its conclusions without undertaking an examination of whether the prorogation had been motivated by an improper purpose of stymieing Parliament. So, contrary to the views expressed by many in the media, the Court did not make a finding that Boris Johnson lied to or misled the Queen.

However, the Court nonetheless expressed clear disquiet at the Prime Minister’s conduct. When considering the documents which had been provided in order to justify the decision, the Court stated that:

Perhaps most tellingly of all, the memorandum does not address the competing merits of going into recess and prorogation. It wrongly gives the impression that they are much the same. The Prime Minister’s reaction was to describe the September sitting as a “rigmarole”. Nowhere is there a hint that the Prime Minister, in giving advice to Her Majesty, is more than simply the leader of the Government seeking to promote its own policies; he has a constitutional responsibility, as we have explained in para 30 above. [60]

The language is soft, but it carries.

What this will mean for Brexit remains unclear. In the immediate term, Parliament will resume and the Court’s decision affirms that the Prime Minister will not be able to set Brexit policy without Parliamentary involvement. It therefore seems that the key question now will be whether the Government and Parliament can agree a way forward to break the Brexit impasse. If they will remain at odds, a general election to try and break the deadlock seems likely.

Jonathan Metzer is a barrister at 1 Crown Office Row. He is commissioning editor of the UK Human Rights Blog.

1 comment;

  1. Why wasn’t the script the BBC broadcast Lady Hale reading yesterday the same as the official, published judgment on the Supreme Court website? In vain I searched the official judgment for the phrases my telly repeatedly showed Ms Hale reading out in the courtroom. What the heck is going on, whereby switching on the BBC news, and reading the official judgement on the Surpreme Court’s own website, presents with me with two completely different scripts? Just asking …

Welcome to the UKHRB

This blog is run by 1 Crown Office Row barristers' chambers. Subscribe for free updates here. The blog's editorial team is:
Commissioning Editor: Jonathan Metzer
Editorial Team: Rosalind English
Angus McCullough QC David Hart QC
Martin Downs
Jim Duffy

Free email updates

Enter your email address to subscribe to this blog for free and receive weekly notifications of new posts by email.




This blog is maintained for information purposes only. It is not intended to be a source of legal advice and must not be relied upon as such. Blog posts reflect the views and opinions of their individual authors, not of chambers as a whole.

Our privacy policy can be found on our ‘subscribe’ page or by clicking here.


Aarhus Abortion Abu Qatada Abuse Access to justice adoption ALBA Al Qaeda animal rights anonymity Article 1 Protocol 1 Article 2 article 3 Article 4 article 5 Article 6 Article 8 Article 9 article 10 Article 11 article 13 Article 14 Artificial Intelligence Asbestos assisted suicide asylum Australia autism benefits Bill of Rights biotechnology blogging Bloody Sunday brexit Bribery Catholicism Chagos Islanders Children children's rights China christianity citizenship civil liberties campaigners climate change clinical negligence Coercion common law confidentiality consent conservation constitution contempt of court Control orders Copyright coronavirus costs Court of Protection crime Cybersecurity Damages data protection death penalty defamation deportation deprivation of liberty Detention disability disclosure Discrimination disease divorce DNA domestic violence duty of care ECHR ECtHR Education election Employment Environment Equality Act Ethiopia EU EU Charter of Fundamental Rights EU costs EU law European Court of Justice evidence extradition extraordinary rendition Family Fertility FGM Finance foreign criminals foreign office France freedom of assembly Freedom of Expression freedom of information freedom of speech Gay marriage Gaza genetics Germany Google Grenfell Health HIV home office Housing HRLA human rights Human Rights Act human rights news Huntington's Disease immigration India Indonesia injunction Inquests international law internet Inuit Iran Iraq Ireland Islam Israel Italy IVF Japan Judaism judicial review jury trial JUSTICE Justice and Security Bill Law Pod UK legal aid Leveson Inquiry LGBTQ Rights liability Libel Liberty Libya Lithuania local authorities marriage mental capacity Mental Health military Ministry of Justice modern slavery music Muslim nationality national security NHS Northern Ireland nuclear challenges Obituary ouster clauses parental rights parliamentary expenses scandal patents Pensions Personal Injury Piracy Plagiarism planning Poland Police Politics pollution press Prisoners Prisons privacy Professional Discipline Property proportionality Protection of Freedoms Bill Protest Public/Private public access public authorities public inquiries rehabilitation Reith Lectures Religion RightsInfo right to die right to family life Right to Privacy right to swim riots Roma Romania Round Up Royals Russia Saudi Arabia Scotland secrecy secret justice sexual offence Sikhism Smoking social media South Africa Spain special advocates Sports Standing statelessness stop and search Strasbourg Supreme Court Supreme Court of Canada surrogacy surveillance Syria Tax technology Terrorism tort Torture travel treaty TTIP Turkey UK Ukraine USA US Supreme Court vicarious liability Wales War Crimes Wars Welfare Western Sahara Whistleblowing Wikileaks wind farms WomenInLaw YearInReview Zimbabwe
%d bloggers like this: