Royal prerogative

The royal prerogative comprises the residue of discretionary or arbitrary authority lawfully vested in the Crown. In Blackstone's formulation it is 'those rights and capacities which the King enjoys alone, in contradistinction to others.' Although historically vast, the prerogative has been steadily confined by both statute and convention, and since the late twentieth century many of its exercises have become subject to judicial review. Today it covers the conduct of foreign affairs, the deployment of armed forces, the grant of honours, the issue and revocation of passports, the prerogative of mercy, certain appointments (including the appointment of ministers), and the prorogation and dissolution of Parliament (though this last is now regulated by the Dissolution and Calling of Parliament Act 2022).

Prerogative powers are part of the common law: they are recognised and defined by the courts, and they may not be extended by the executive unilaterally. This note examines the historical evolution of the prerogative, its legal characteristics, the justiciability revolution inaugurated by GCHQ and continued in Fire Brigades Union and Miller, and the ongoing academic debates about whether the prerogative is best understood as anachronistic, as necessary flexibility in the modern state, or as an instrument requiring urgent constitutional reform.

Three themes should be borne in mind throughout. First, the prerogative interacts with parliamentary sovereignty: statute trumps prerogative, and the executive may not use prerogative powers to alter statute or to frustrate statutory purpose (De Keyser's Royal Hotel; Fire Brigades Union). Second, the prerogative sits uneasily with the rule of law: many exercises are discretionary, non-statutory, and until recently were thought to lie beyond the supervisory jurisdiction of the courts. Third, the development of judicial review of the prerogative marks an important shift in the separation of powers, rebalancing executive authority against legal accountability. Understanding these dynamics is essential to appreciating the contemporary constitution.

The prerogative is rooted in the feudal conception of kingship. In medieval England the monarch was both the supreme landlord and the fount of justice. Certain powers inhered in the Crown ex officio—making war and peace, granting honours, coining money, summoning and dissolving Parliament—powers justified by the personal, divinely ordained authority of the sovereign. The struggle between Crown and Parliament in the seventeenth century was in large part a struggle over the scope and control of prerogative powers.

The Case of Proclamations (1611) established that the King could not by proclamation create new offences or alter the common law. As Coke CJ put it, 'the King hath no prerogative, but that which the law of the land allows him.' The Crown's claim to absolute prerogative was a principal cause of the Civil War. The Bill of Rights 1689 declared unlawful the power to suspend or dispense with laws, and entrenched the requirement for parliamentary consent to taxation. These constitutional settlements confined the prerogative within law but did not abolish it.

By the nineteenth century Dicey was able to write that 'every act which the executive government can lawfully do without the authority of an Act of Parliament is done in virtue of this prerogative.' That description remains broadly accurate today, though the scope of the prerogative has narrowed progressively. Many former prerogative functions—the conduct of war (to some extent), the civil service, the granting of passports—are now overlaid or displaced by statute. The twentieth century saw a gradual shift from viewing the prerogative as the personal will of the monarch to recognising it as exercised by ministers on the advice of government, subject to convention and, latterly, to law.

The transformation of the prerogative from untouchable royal discretion into a justiciable part of public law is recent. Until 1985 it was widely assumed that exercises of prerogative power lay outside the courts' supervisory jurisdiction. GCHQ changed that orthodoxy, opening the door to legal challenge on the grounds of illegality, irrationality, and procedural impropriety. The subsequent case law—Fire Brigades Union, Northumbria Police, the two Miller decisions, and Prorogation—represents one of the most significant developments in modern constitutional law.

1. Definition and nature

The prerogative consists of the residual legal powers and immunities belonging to the Crown. It is part of the common law. The courts recognise and delimit prerogative powers; they will not permit the executive to assert new or enlarged prerogatives (BBC v Johns). In R v Secretary of State for the Home Department, ex parte Northumbria Police Authority Purchas LJ stated that the courts are the 'constitutional umpire' determining the existence and extent of prerogative powers.

The prerogative is to be distinguished from the Crown's ordinary common-law capacities (such as the capacity to enter contracts or own property). The latter are enjoyed by all legal persons; the former are unique to the Crown.

2. Categories of prerogative power

The main surviving prerogatives include:

• Foreign affairs: treaty-making, recognition of states, deployment of armed forces abroad.
• Domestic executive powers: appointment and dismissal of ministers, grant of honours, issue and revocation of passports, prerogative of mercy.
• Parliament: historically summoning, proroguing and dissolving Parliament (though dissolution is now statutory).
• Justice: the Attorney-General's power to enter a nolle prosequi, the prerogative of mercy.
• Defence: organisation and deployment of the armed forces (but declaration of war is increasingly understood to require parliamentary approval by convention).

3. Prerogative and statute: the principle of abeyance

The case law on the prerogative is central to understanding the modern constitution. Five decisions stand out.

Attorney-General v De Keyser's Royal Hotel Ltd [1920] established the fundamental principle that statute displaces prerogative. During the First World War the Crown requisitioned a hotel under prerogative powers, paying no compensation. The Defence of the Realm Act 1842 provided for compensation. The House of Lords held that where Parliament has enacted detailed provisions covering the same ground as a prerogative, the prerogative cannot be invoked to avoid statutory conditions. The statute prevails, and the prerogative is in abeyance.

Council of Civil Service Unions v Minister for the Civil Service [1985] (GCHQ) transformed the justiciability of prerogative power. The Home Secretary used the prerogative to ban trade union membership at GCHQ without prior consultation. The House of Lords held that exercises of prerogative power are reviewable in principle on the same public law grounds as statutory powers. Although the claim failed on national security grounds, the ratio was clear: prerogative is not immune from judicial review. Lord Diplock's threefold classification—illegality, irrationality, procedural impropriety—applies to prerogative as to statute.

R v Secretary of State for the Home Department, ex parte Fire Brigades Union [1995] further limited executive reliance on prerogative. The Criminal Justice Act 1988 provided for a statutory criminal injuries compensation scheme but had not been brought into force. The Home Secretary introduced a cheaper non-statutory scheme under the prerogative. The House of Lords held this unlawful: by introducing a scheme inconsistent with the statute, the minister had acted to frustrate Parliament's intent. The prerogative cannot be used to pre-empt or undermine a statutory scheme, even one not yet commenced.

R (Miller) v Secretary of State for Exiting the European Union [2017] (Miller I) concerned whether the Government could trigger Article 50 TEU to withdraw from the EU by prerogative alone. The Supreme Court held it could not. The European Communities Act 1972 had conferred rights on individuals enforceable in domestic law. Only Parliament could authorise their removal. The Crown could not use prerogative powers to change domestic law or nullify rights conferred by statute. The decision reaffirmed the primacy of statute over prerogative and the principle that ministers act within, not above, the law.

R (Miller) v The Prime Minister; Cherry v Advocate General for Scotland [2019] (Miller II or the Prorogation case) addressed whether the Prime Minister's advice to the Queen to prorogue Parliament for five weeks was lawful. The Supreme Court held unanimously that the advice was unlawful because it had the effect of frustrating Parliament's constitutional functions without reasonable justification. Crucially, the Court held that the existence and limits of prerogative powers are always questions of law for the courts, even if the manner of exercise may sometimes be non-justiciable. The decision marked the high-water mark of judicial oversight of the executive's use of prerogative.

These cases illustrate the courts' willingness to police the boundaries of prerogative power, to insist on statutory supremacy, and to protect constitutional principles—particularly parliamentary sovereignty and the rule of law—from executive overreach.

See practice questions below.

See further reading below.