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

Introduction

R (Miller) v The Prime Minister [2019] UKSC 41 (also known as Cherry v Advocate General for Scotland) is a historic constitutional case concerning the prorogation of Parliament. In an unprecedented unanimous decision, the Supreme Court held that the advice given by the Prime Minister to Her Majesty The Queen to prorogue Parliament for five weeks was unlawful because it had the effect of frustrating the constitutional role of Parliament. The case is a landmark on the justiciability of prerogative powers and the constitutional limits on executive power.

The Facts

In August 2019, the Prime Minister, Boris Johnson, advised the Queen to prorogue Parliament from 9 September until 14 October 2019. The prorogation would have limited parliamentary time for scrutiny of the government’s Brexit plans before the exit date of 31 October 2019. The claimants argued that the prorogation was unlawful because its purpose was to prevent Parliament from scrutinising the government.

The Judgment

The Supreme Court held unanimously that the prorogation was unlawful. The court held that the question of whether the Prime Minister’s advice was lawful was justiciable — it was not a non-justiciable political question. The court identified the constitutional principles that Parliament is sovereign and that the government is accountable to Parliament. A prorogation that has the effect of frustrating Parliament’s constitutional role without reasonable justification is unlawful.