R (Miller) v The Prime Minister; Cherry v Advocate General for Scotland

Facts

On 28 August 2019, the Prime Minister, Boris Johnson, advised the Queen to prorogue Parliament, ending the parliamentary session, from a date between 9 and 12 September until 14 October 2019. That meant Parliament wouldn't sit for five weeks during a critical period, with the UK due to leave the EU on 31 October.

Challenges were brought in England (by Gina Miller) and in Scotland (by Joanna Cherry MP and others). The English Divisional Court held that the matter was non-justiciable. The Inner House of the Court of Session in Scotland held that it was justiciable and the prorogation was unlawful. Both cases went to the Supreme Court.

Issues

• Was the lawfulness of the Prime Minister's advice to prorogue justiciable?
• If so, what was the legal standard for judging whether it was lawful?
• Was the prorogation lawful, and if not, what was the remedy?

Decision

The Supreme Court, sitting as a panel of eleven justices, held unanimously that the prorogation was unlawful, and that the Order in Council proroguing Parliament was void and of no effect. Parliament had not been prorogued. Lady Hale and Lord Reed gave a joint judgment for the whole Court.

Reasoning

Justiciability. The Court drew a distinction between the existence and extent of a prerogative power, which the courts have always decided, and the manner of its exercise within those limits. The question here was about the limits of the power to prorogue, so it was a legal question for the courts. The fact that the issue was politically controversial didn't make it non-justiciable.

The constitutional principles. The limits of the power to prorogue had to be compatible with fundamental constitutional principles:

• Parliamentary sovereignty: an unlimited power to prorogue would let the executive prevent Parliament from legislating for as long as it wished.
• Parliamentary accountability: ministers are accountable to Parliament, and an extended prorogation would stop Parliament from holding them to account.

The test. A decision to prorogue is unlawful if it has the effect of frustrating or preventing, without reasonable justification, Parliament's ability to carry out its constitutional functions as a legislature and as the body responsible for supervising the executive.

Applying the test. The prorogation's effect was extreme: Parliament was prevented from sitting for five of the eight weeks before the scheduled exit date, at a time of fundamental constitutional change. No reasonable justification had been offered for such a long prorogation. The advice was therefore unlawful.

Remedy. Because the prorogation wasn't a "proceeding in Parliament", Article 9 of the Bill of Rights 1689 didn't prevent the court from ruling on it. The Order in Council was void, and Parliament resumed sitting on 25 September 2019.

Why it matters

Miller (No 2) is one of the most significant constitutional decisions of recent times. It shows the courts using fundamental principles to define the limits of prerogative power, and it builds on Entick v Carrington (1765) and the Case of Proclamations (1611).

Parliament later passed the Dissolution and Calling of Parliament Act 2022, which revived the prerogative power to dissolve Parliament and included a clause ousting the courts' jurisdiction to review its exercise. The Act doesn't address prorogation.

How it comes up in exams

Use Miller (No 2) for questions on:

1. Justiciability: distinguish the limits of a power (reviewable) from its exercise within those limits.
2. The constitutional principles that shape the prerogative: parliamentary sovereignty and accountability.
3. The separation of powers and the courts' role in a constitution without a single written text.
4. Ouster clauses and the courts' approach to them, comparing the 2022 Act with R (Privacy International) v Investigatory Powers Tribunal [2019] UKSC 22.

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