R (on the application of Miller) v The Prime Minister

A prerogative decision to prorogue Parliament is unlawful where it frustrates or prevents, without reasonable justification, Parliament’s ability to legislate and supervise the executive. The court will intervene where that effect is sufficiently serious.

Determining the existence and legal limits of a prerogative power is a judicial function. Political controversy and ministerial accountability to Parliament do not exclude legal accountability. Parliamentary sovereignty and parliamentary accountability constrain the power of prorogation.

An unlawful recommendation to prorogue is null and produces no legal effect. Prorogation is imposed upon Parliament and terminates its essential business; it is not itself a proceeding in Parliament protected by parliamentary privilege.

The Prime Minister advised the Queen to prorogue Parliament from a date between 9 and 12 September 2019 until 14 October 2019. The prorogation would prevent Parliament from sitting during five of the eight weeks between the end of its summer recess and the date then fixed for the United Kingdom’s departure from the European Union.

Mrs Gina Miller challenged the advice in England and Wales. The Divisional Court dismissed her claim as non-justiciable: [2019] EWHC 2381 (QB). In parallel Scottish proceedings brought by Joanna Cherry MP and others, the Lord Ordinary dismissed the petition, but the Inner House allowed the appeal and held the advice and ensuing prorogation unlawful and null: [2019] CSIH 49.

The Supreme Court considered whether the lawfulness of the advice was justiciable, the governing legal standard, whether the advice satisfied that standard, and the appropriate remedy.

1. Disposition. The court unanimously allowed Mrs Miller’s appeal and dismissed the Advocate General’s appeal in Cherry. It declared that the Prime Minister’s advice, the resulting Order in Council and the purported prorogation were unlawful, null and of no effect. Parliament had not been prorogued.

2. Justiciability. Courts have jurisdiction to determine whether a prerogative power exists and where its legal limits lie. That remains so where the dispute has political consequences. Political accountability to Parliament does not replace ministers’ legal accountability to the courts. Judicial enforcement of the legal boundary between the executive and Parliament gives effect to, rather than offends, the separation of powers.

3. Constitutional limits. Prerogative powers are recognised by the common law and must be compatible with constitutional principles. Parliamentary sovereignty would be undermined if the executive could prevent Parliament from exercising its legislative authority for as long as it pleased. Parliamentary accountability would likewise be endangered if prorogation could replace responsible government with unaccountable government.

4. Governing standard. A decision to prorogue Parliament, or to advise the monarch to do so, is unlawful if it frustrates or prevents, without reasonable justification, Parliament’s ability to perform its constitutional functions as legislature and supervisor of the executive. The court will intervene where the effect is sufficiently serious. A customary short prorogation will normally be justified by the wish to end one session and begin another. Any further justification must be assessed cautiously and with sensitivity to the Prime Minister’s responsibilities and political judgment.

5. Application. The five-week prorogation had an extreme effect. It prevented Parliament from performing its constitutional role during a critical period preceding a fundamental constitutional change. The documents before the court explained why a Queen’s Speech was proposed for 14 October, but gave no reason why Parliament needed to be closed for five weeks. The evidence did not establish any reasonable justification. The advice was therefore outside the Prime Minister’s powers and unlawful.

6. Privilege and remedy. Under article 9 of the Bill of Rights 1688, courts determine the scope of parliamentary privilege. Prorogation is not a proceeding in Parliament: it is imposed from outside, is not decided or debated by either House, and terminates Parliament’s essential business. Article 9 therefore did not prevent review. The unlawful advice was null, the Order in Council founded upon it was quashed, and the purported prorogation had no effect. It was for Parliament, through its presiding officers, to decide what to do next.

1. United Kingdom Supreme Court: The court unanimously allowed Mrs Miller’s appeal from [2019] EWHC 2381 (QB) and dismissed the Advocate General’s appeal from [2019] CSIH 49. It held that the advice and purported prorogation were unlawful, null and of no effect.

2. Inner House of the Court of Session: In [2019] CSIH 49, the court allowed the appeal from the Lord Ordinary. It held that the advice was justiciable, was motivated by the improper purpose of stymying parliamentary scrutiny, and was unlawful and null.

3. Lord Ordinary: In [2019] CSOH 70, Lord Doherty dismissed the petition as non-justiciable, having earlier refused interim interdict in [2019] CSOH 68.

4. Divisional Court of the High Court: In [2019] EWHC 2381 (QB), the court dismissed Mrs Miller’s claim as non-justiciable and granted a leapfrog certificate.