R (Miller) v Prime Minister [2019] UKSC 41

The Prime Minister advised the Queen to prorogue Parliament for five weeks during the critical Brexit period. The Supreme Court unanimously held this advice was unlawful as it frustrated Parliament's constitutional functions without reasonable justification. The prorogation was declared null and of no effect.

Facts

In August 2019, Prime Minister Boris Johnson advised Her Majesty the Queen to prorogue Parliament from a date between 9th and 12th September until 14th October 2019. This occurred during a critical period before the United Kingdom’s scheduled exit from the European Union on 31st October 2019. The prorogation would have prevented Parliament from sitting for five weeks, significantly longer than the usual short prorogation period. Two separate legal challenges were brought: one in Scotland (Cherry) and one in England (Miller), which reached conflicting conclusions before being heard together by the Supreme Court.

Background Context

Following the 2016 referendum, the UK was due to leave the EU. Parliament had rejected the withdrawal agreement three times. A majority in the House of Commons opposed withdrawal without an agreement. The Prime Minister had made clear his negotiating strategy required a credible risk of no-deal Brexit.

Issues

The Supreme Court identified four key issues:

• Whether the Prime Minister’s advice to the Queen was justiciable in a court of law
• By what standard the lawfulness of the advice should be judged
• Whether the advice was lawful by that standard
• What remedy the court should grant

Judgment

The Supreme Court, sitting as eleven Justices, ruled unanimously that the Prime Minister’s advice was unlawful, null and of no effect.

On Justiciability

The Court firmly rejected arguments that the matter was non-justiciable. Lady Hale and Lord Reed, delivering the judgment of the Court, stated:

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.

The Legal Standard

The Court established that the power to prorogue is limited by fundamental constitutional principles, particularly Parliamentary sovereignty and Parliamentary accountability. The Court held:

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.

Application to the Facts

The Court found that prorogation prevented Parliament from carrying out its constitutional role for five out of eight possible weeks before exit day. No reasonable justification was provided for this exceptional length:

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.

On Remedy

The Court declared the advice unlawful and null, the Order in Council unlawful and to be quashed, and the prorogation itself null and of no effect:

It follows that Parliament has not been prorogued and that this court should make declarations to that effect.

Implications

This landmark decision established that prerogative powers relating to Parliament are subject to judicial review where they affect fundamental constitutional principles. The judgment reinforced that the executive cannot use prerogative powers to frustrate Parliament’s constitutional functions. It confirmed that while courts respect the separation of powers, they have a constitutional duty to determine the legal limits of governmental power, even in politically sensitive contexts. The case represents a significant development in constitutional law, clarifying the relationship between executive prerogative and Parliamentary sovereignty.

Verdict: The Supreme Court unanimously allowed Mrs Miller’s appeal and dismissed the Advocate General’s appeal in Cherry. The Court declared that the Prime Minister’s advice to Her Majesty was unlawful, null and of no effect; that the Order in Council was unlawful and should be quashed; and that the prorogation was null and of no effect, meaning Parliament had not been prorogued.

Source: R (Miller) v Prime Minister [2019] UKSC 41