R (Miller) v The Prime Minister; Cherry v Advocate General for Scotland [2019] UKSC 41
Supreme Court, 24 September 2019. Also reported at [2020] AC 373.
The Supreme Court unanimously held that the Prime Minister’s advice to prorogue Parliament for five weeks was unlawful. Its effect was to prevent Parliament from performing its constitutional functions without reasonable justification. The advice, the resulting Order in Council and the purported prorogation were legally ineffective: Parliament had not been prorogued.
The events and the two appeals
In August 2019, the Government proposed ending the parliamentary session and beginning a new one with a Queen’s Speech on 14 October. On 28 August, an Order in Council provided for prorogation to start between 9 and 12 September and continue until 14 October. At that time, the United Kingdom was scheduled to leave the European Union on 31 October.
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A group led by Joanna Cherry had already begun Scottish proceedings on 30 July because of concerns that prorogation might be used to prevent parliamentary debate before the scheduled departure. Gina Miller began proceedings in England after the proposed prorogation was announced.
The Divisional Court in England dismissed Miller’s claim on the ground that the issue was not justiciable: it considered that there were no legal standards against which to assess the decision. The Inner House of the Court of Session reached a different conclusion. It held that the advice was justiciable and had the improper purpose of obstructing parliamentary scrutiny.
The Supreme Court heard Miller’s appeal and the Advocate General’s appeal in Cherry together before eleven justices. The questions concerned the courts’ power to review the advice, the applicable legal limits, whether those limits had been exceeded, and the appropriate remedy.
Why the question was justiciable
Prorogation was a prerogative power recognised by the common law. The Court distinguished deciding the existence and extent of such a power from reviewing its exercise within its lawful limits. Determining the power’s legal boundaries was unquestionably a judicial function.
The political context did not remove that function. Courts had long determined the legality of executive action, including in politically contentious circumstances. The Prime Minister’s accountability to Parliament was not a substitute for accountability to the courts on questions of law. Moreover, prorogation itself interrupted parliamentary scrutiny.
The Court therefore approached the case as a question about the limits of the power, not as an invitation to choose between competing political policies. Enforcing those limits would protect the separation of powers by preserving Parliament’s ability to perform its own role.
The constitutional limit
Two principles supplied the relevant boundary. Parliamentary sovereignty would be undermined if the executive could prevent Parliament from legislating for as long as it wished. Parliamentary accountability would likewise be undermined if ministers could avoid questions, committee scrutiny and other forms of supervision through a prolonged suspension of Parliament.
The Court held that prorogation, or advice to prorogue, would be unlawful where its effect was to frustrate or prevent Parliament’s legislative and supervisory functions without reasonable justification. Judicial intervention required an effect sufficiently serious to justify that exceptional step.
This did not make every prorogation unlawful. A short interruption to end one session and begin another would normally be justified. The Court also recognised the Prime Minister’s responsibilities and the need for caution when assessing an explanation involving political judgment. The legal question remained whether the power’s limits had been exceeded.
Why this prorogation was unlawful
The proposed interruption covered five of the eight weeks between the end of the summer recess and the scheduled EU departure. It prevented ordinary legislation and parliamentary scrutiny at a particularly important time. The possibility that Parliament might otherwise have taken a conference recess did not make the two arrangements equivalent: during a recess, committees and written questions could continue.
The Government’s documents explained the wish for a new legislative programme and the chosen date of the Queen’s Speech. They did not explain why preparation required Parliament to be prorogued for five weeks. The Court could not supply missing reasons through speculation.
The advice was therefore unlawful because of the serious effect on Parliament and the absence of reasonable justification for that effect. The Supreme Court did not need to determine the separate challenge based on the Prime Minister’s alleged improper motive. This distinguishes its reasoning from the Inner House’s approach.
The remedy and appeal outcomes
The Government argued that parliamentary privilege prevented the Court from questioning the prorogation. The Court rejected that argument. Although the ceremony took place in Parliament, prorogation was imposed on the Houses from outside; it was not a decision on which their members could debate or vote. Article 9 of the Bill of Rights 1688 did not shield it from review.
The unlawful advice was outside the Prime Minister’s powers. The Order in Council founded upon it was likewise unlawful and had to be quashed. The purported prorogation had no legal effect. Parliament did not require a statutory recall; the Speakers could take steps to enable the Houses to meet and decide what to do next.
Miller’s appeal was allowed and the Advocate General’s appeal in Cherry was dismissed, with the same declarations and orders in both cases. The judgment concerned the legality of prorogation, not whether or on what terms the United Kingdom should leave the European Union.
Source: Full Supreme Court judgment, especially paragraphs 15–27, 30–52 and 55–71.
