Royal Prerogative

The Royal Prerogative is a body of customary authority recognised by the common law as belonging to the Crown. In the United Kingdom, it covers powers that have not been replaced by statute, including the conduct of foreign affairs, the deployment of the armed forces, the making and ratification of treaties, the granting of honours, the issuance and revocation of passports, the prerogative of mercy, and the appointment of ministers. Although nominally vested in the monarch, in modern constitutional practice nearly all prerogative powers are exercised by the Prime Minister and Cabinet on behalf of the sovereign, under the convention of responsible government.

A.V. Dicey, in Introduction to the Study of the Law of the Constitution (1885), defined the prerogative as "the residue of discretionary or arbitrary authority which at any given time is legally left in the hands of the Crown." Parliament can abolish or restrict any prerogative power by statute, and the courts can review its existence and scope.

Key judicial limits include the Case of Proclamations (1611), which held the King could not create new offences by proclamation, and the Council of Civil Service Unions v Minister for the Civil Service (1985), the "GCHQ case," which confirmed that exercise of prerogative powers is in principle subject to judicial review. In R (Miller) v Secretary of State for Exiting the European Union (2017), the UK Supreme Court ruled the government could not use prerogative powers to trigger Article 50 TEU without parliamentary authorisation. In R (Miller) v The Prime Minister (2019), the Court held the advice to prorogue Parliament was unlawful.

Some prerogatives have been placed on statutory footing — for example, civil service management under the Constitutional Reform and Governance Act 2010, which also codified treaty ratification procedures. Similar prerogative frameworks operate in Canada, Australia, and New Zealand, exercised by the Governor-General.