Prerogative Power
Residual powers of the Crown exercised by ministers without statutory authority, including treaty-making, deployment of armed forces, and the prerogative of mercy. Subject to judicial review (GCHQ case [1985]; Miller v Secretary of State [2017]).
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
The Supreme Court's judgment in R (Miller) v The Prime Minister described a prerogative power as a power recognised by the common law and exercised by the Crown, in this instance by the sovereign in person, acting on advice, in accordance with modern constitutional practice. Unlike a statutory power, it is not created or defined by any document, so its limits are worked out by the courts case by case.
That prerogative powers are subject to legal limits set by the courts is not a modern innovation. The Supreme Court traced the principle back to the Case of Proclamations (1611), where the court concluded that 'the King hath no prerogative, but that which the law of the land allows him', establishing that the limits of prerogative powers were set by law and determined by the courts — a principle the Court applied in 2019 to hold that the advice to prorogue Parliament was itself unlawful.
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Official sources
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