Royal prerogative in the United Kingdom

British passports and chivalric orders are regulated under the royal prerogative.

The royal prerogative is a body of customary authority, privilege, and immunity, recognised in the United Kingdom as the sole prerogative of the Sovereign and the source of many of the executive powers of the British government.

Prerogative powers were formerly exercised by the monarch acting on his or her own initiative. Since the 19th century, by convention, the advice of the prime minister or the cabinet—who are then accountable to Parliament for the decision—has been required in order for the prerogative to be exercised. The monarch remains constitutionally empowered to exercise the royal prerogative against the advice of the prime minister or the cabinet, but in practice would only do so in emergencies or where existing precedent does not adequately apply to the circumstances in question.

Today the royal prerogative is available in the conduct of the government of the United Kingdom, including foreign affairs, defence, and national security. The monarchy has a significant constitutional presence in these and other matters, but limited power, because the exercise of the prerogative is in the hands of the prime minister and other ministers or other government officials.

The royal prerogative has been called "a notoriously difficult concept to define adequately", but whether a particular type of prerogative power exists is a matter of common law to be decided by the courts as the final arbiter. A prominent constitutional theorist, A. V. Dicey, proposed in the nineteenth century that:

The prerogative appears to be historically and as a matter of fact nothing else than the residue of discretionary or arbitrary authority which at any given time is legally left in the hands of the crown. The prerogative is the name of the remaining portion of the Crown's original authority ... Every act which the executive government can lawfully do without the authority of an Act of Parliament is done in virtue of the prerogative.

While many commentators follow the Diceyan view, there are constitutional lawyers who prefer the definition given by William Blackstone in the 1760s:

By the word prerogative we usually understand that special pre-eminence which the King hath, over and above all other persons, and out of the ordinary course of common law, in right of his regal dignity ... it can only be applied to those rights and capacities which the King enjoys alone, in contradiction to others, and not to those which he enjoys in common with any of his subjects.