Factual and Procedural Background
A referendum held on 23 June 2016 produced a vote for the United Kingdom to leave the European Union. Subsequent Governments pursued withdrawal and, after legislative steps such as the European Union (Withdrawal) Act 2018, exit day was set for 31 October 2019. On 28 August 2019 the Defendant, as Prime Minister, advised The Queen to prorogue Parliament from a date between 9 and 12 September until 14 October 2019. Parliament would therefore lose up to five sitting weeks during a critical period before exit day.
Litigation began in Scotland on 30 July 2019, where a cross-party group of parliamentarians (the “Cherry” action) sought to prevent such a prorogation. The Outer House dismissed the claim on non-justiciability grounds, but the Inner House reversed that decision on 11 September 2019, declaring the advice and the resulting prorogation unlawful. Meanwhile, the Plaintiff in England and Wales (the “Miller” action) brought similar proceedings; the Divisional Court dismissed that claim on 11 September 2019, also on non-justiciability grounds.
Given the conflicting decisions, the Supreme Court convened a panel of 11 Justices – the maximum permitted – and heard combined appeals from 17 to 19 September 2019.
Legal Issues Presented
- Whether the lawfulness of the Defendant’s advice to prorogue Parliament is justiciable.
- The legal standard by which the propriety of such advice should be judged.
- Applying that standard, whether the advice was lawful.
- The appropriate remedy if the advice was unlawful.
Arguments of the Parties
Appellant’s Arguments (Government)
- The matter is non-justiciable; prorogation is a high-level political judgment for which the Defendant is accountable to Parliament, not the courts.
- There are no legal standards by which a court can assess the duration or timing of prorogation.
- Intervention would breach the constitutional separation of powers.
Respondents’ Arguments (Parliamentarians and Citizen Claimants)
- The advice is reviewable because it involves defining the limits of a prerogative power.
- Prorogation for five weeks in the immediate run-up to exit day frustrates Parliament’s constitutional functions of legislation and executive scrutiny.
- No reasonable justification was offered; evidence from a Former Prime Minister indicated that preparing a Queen’s Speech typically requires only four to six days.
Table of Precedents Cited
| Precedent |
Rule or Principle Cited For |
Application by the Court |
| Case of Proclamations (1611) |
“The King hath no prerogative but that which the law of the land allows.” |
Illustrated that defining the limits of prerogative powers is a judicial function. |
| Entick v Carrington (1765) |
Executive cannot interfere with property without lawful authority. |
Example of courts reviewing executive action despite political controversy. |
| Council of Civil Service Unions v Minister for the Civil Service (1985) |
Courts may determine the existence and extent of prerogative powers. |
Relied on to show that questions about prerogative limits are justiciable. |
| R v Secretary of State for the Home Department, ex p Fire Brigades Union (1995) |
Executive cannot use prerogative to bypass Parliamentary legislation. |
Cited to emphasise Parliamentary sovereignty and judicial enforcement. |
| Attorney General v De Keyser’s Royal Hotel Ltd (1920) |
Statute overrides conflicting use of prerogative powers. |
Supported the principle that prerogative is limited by law. |
| Burmah Oil Co Ltd v Lord Advocate (1965) |
Property cannot be taken under prerogative without compensation. |
Demonstrated constitutional limits on prerogative. |
| R (Miller) v Secretary of State for Exiting the EU (2017) |
Parliamentary approval is required for fundamental constitutional change; Parliamentary accountability is fundamental. |
Reinforced the constitutional principles applied in the present case. |
| R v Chaytor (2010) |
Court’s role in determining scope of Parliamentary privilege. |
Used to reject the argument that Article 9 of the Bill of Rights barred review. |
| R (UNISON) v Lord Chancellor (2017) |
Measures impeding constitutional principles require reasonable justification. |
Framework for assessing whether prorogation’s effect was legally defensible. |
Court's Reasoning and Analysis
Justiciability: The Court, led by Judge Hale and Judge Reed, held that determining the limits of a prerogative power is inherently a legal question. Therefore, the lawfulness of the advice was justiciable.
Constitutional Principles: Two core principles informed the analysis:
- Parliamentary Sovereignty – legislation enacted by Parliament is the supreme law and cannot be frustrated by the executive.
- Parliamentary Accountability – the Government is answerable to Parliament; extended prorogation undermines this accountability.
Legal Standard: A prorogation is unlawful if it frustrates or prevents Parliament from carrying out its constitutional functions without reasonable justification.
Application to the Facts:
- The five-week prorogation removed five of the eight available sitting weeks before exit day, materially inhibiting legislative scrutiny and action.
- No evidence showed that five weeks were needed to prepare the legislative programme; typical preparations take fewer than ten days.
- Documents before the Court revealed no cogent reason for the exceptional length; references to the September sitting as a “rigmarole” suggested disregard for Parliament’s role.
Accordingly, the advice exceeded the legal limits of the prorogation power and was unlawful.
Remedy: Unlawful advice is null. Consequently, the Order in Council and the purported prorogation based on that advice were void ab initio. Parliament, therefore, had not been prorogued and could immediately resume its business.
Holding and Implications
HOLDING: ADVICE UNLAWFUL; PROROGATION VOID.
The appeal by the Appellant (Government) was dismissed; the cross-appeals by the Respondents were allowed. Parliament was deemed never to have been prorogued.
Implications: The decision restored Parliament’s ability to sit and scrutinise the executive during the pre-exit period and confirmed that courts may police the constitutional boundaries of prerogative powers. While the judgment applies to an unprecedented set of facts, it underscores that any future use of prorogation is subject to judicial review when it threatens core constitutional principles.