Prorogation of Parliament Unlawful, holds the Supreme Court

Cloisters’ Head of Public Law, Sheryn Omeri, comments on the historic decision in R (on the application of Miller) v The Prime Minister & Ors [2019] UKSC 41

As long ago as 1748, French political philosopher, Charles de Montesquieu wrote: constant experience shows us that every man invested with power is apt to abuse it…it is necessary from the very nature of things that power should be a check to power.”

Today, the Supreme Court of the United Kingdom admirably discharged its role as one of the three arms of a democratic government responsible for checking the power of another. It held that the advice given to the Queen by Prime Minister Boris Johnson to prorogue (suspend) UK Parliament for a period of 5 weeks in the lead-up to the date by which the UK is due to exit the European Union, namely 31 October 2019, was unlawful.

There was not a single dissenting voice on the Supreme Court, which on this occasion, comprised 11 Justices, the maximum number of those serving who are permitted to preside over a given case.


In the Supreme Court’s judgment, delivered by its first woman President, Lady Hale, the Court reminded us that Parliament does not decide when it should be prorogued; instead, this is a prerogative power exercised by The Crown on the advice of the Privy Council. In practice it is the Government which advises The Crown to prorogue and that advice is heeded. So in substance, the Executive (in this case the Prime Minister) determines whether Parliament can sit for a given period and carry out its usual functions as law-making representative of the people. As a result, in providing the relevant advice, the Prime Minister has a constitutional responsibility to have regard to all relevant interests, including the interests of Parliament.

Parliament’s interests

Parliament’s interests were manifested when the European Union (Withdrawal) Act 2018 came into force on 26 June 2018. Section 13 of the Act requires Parliamentary approval of any withdrawal agreement reached by the Government. Parliament has also demonstrated that a majority of the House of Commons will not support a withdrawal without agreement (ie ‘a no-deal Brexit’).

But when Boris Johnson took over as Prime Minister, he made clear his belief that the European Council will only agree to changes in the withdrawal agreement negotiated by previous PM, Theresa May if it considers there to be a genuine risk that the UK will leave without any such agreement.


The Supreme Court held that although the courts are not generally permitted to decide political questions, the fact that a legal dispute concerns the conduct of politicians, or arises from a matter of political controversy is not a sufficient reason for the courts to refuse to consider it. Further, the fact that in the democratic tradition, the Prime Minister is accountable to Parliament, does not in itself justify the conclusion that the courts have no legitimate role to play for two reasons: first, the effect of prorogation is to prevent the operation of ministerial accountability to Parliament during the period during which Parliament is suspended, so with Parliament prorogued, it was unable to hold Prime Minister Johnson to account. Secondly, in any event, it is the duty of the courts to give effect to the law even if a minister is also accountable to Parliament.

The Supreme Court ultimately held that the sovereignty of Parliament, as the foundational principle of the UK constitution would be undermined if the Executive could, through the use of the prerogative, prevent Parliament from exercising its legislative authority for as long as it pleased. The longer Parliament stands prorogued, the greater the risk that responsible government may be replaced by unaccountable government. For this reason an unlimited power of prorogation by the Executive would be incompatible with Parliamentary sovereignty. So, contrary to the Prime Minister’s arguments made to the Supreme Court, there must be limits on the power to prorogue (or to advise to prorogue). It is at those limits that Supreme Court stands guardian. Having analysed the question in this way, the Supreme Court held that it was “firmly of the opinion” that the question of whether the advice to prorogue was lawful was one with which the Court could deal. For it to do so would not be an interference with the lawful exercise of the power, within its limits.

The Supreme Court was also not prevented from addressing the question by Article 9 of the Bill of Rights of 1688 which disallows questioning of any proceedings in Parliament in any court. The Supreme Court sensibly held that while prorogation takes place in Parliament, it does not amount to ‘proceedings in Parliament’ since it is not a decision of either House of Parliament but rather something imposed on them by the Executive. It is not core or essential business of Parliament. Instead, it brings such business to an end.

Limit of the power to prorogue

The Supreme Court defined the limit as the point at which the decision to prorogue 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. The related question of whether, in any given circumstances, prorogation frustrated Parliament in this way is one of fact. The Supreme Court held that in the present circumstances the answer to this question is: “of course it did.” A fundamental change was due to take place in the constitution of the UK on 31 October 2019. The House of Commons, comprising the democratically elected representatives of the people, has a right to have a voice in how that change comes about.

Prime Minister’s reasons for advising prorogation

The Supreme Court said it was not concerned with the Prime Minister’s motive in advising The Queen to prorogue Parliament but whether he had reasonable justification for doing so. It found that he did not. It said: “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…It is impossible for us to conclude…that there was any reason – let alone a good reason – to advise Her Majesty to prorogue Parliament for five weeks…It follows that the decision was unlawful.”

In so holding, the Supreme Court made clear that its decision was giving effect to the principle of the separation of powers. This must be right, since by ensuring that Parliament is not unlawfully prorogued, the Supreme Court was doing no more than resurrecting the third arm of democratic government which had been sought to be temporarily killed off by another and at this, most crucial time in the country’s history. In this way the Supreme Court was also acknowledging another of Montesquieu’s observations, that if the legislative and executive authorities are one institution, there will be no freedom.