Royal prerogative and Miller (Nos 1 and 2)

The royal prerogative—the residue of discretionary power legally remaining with the Crown—is subordinate to statute and reviewable by courts. Five key principles govern: (1) prerogative cannot override statute (Case of Proclamations; De Keyser); (2) exercise of prerogative is reviewable subject to justiciability limits (GCHQ); (3) prerogative cannot remove statutory rights (Miller No 1); (4) prerogative advice to the Monarch must comply with constitutional principle (Miller No 2); (5) no new prerogatives can be created (BBC v Johns). The rationale is that all governmental power, including ancient Crown powers, must operate within legal limits enforced by courts to protect parliamentary sovereignty and the rule of law.

Case of Proclamations (1610) 12 Co Rep 74: The King cannot by proclamation change law or create offences; prerogative exists only as law allows. Foundational limit on Crown power. Attorney-General v De Keyser's Royal Hotel Ltd [1920] AC 508: Statute displaces prerogative in same field; Crown cannot bypass statutory scheme requiring compensation. Establishes 'abeyance' doctrine. Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374: Exercise of prerogative reviewable on public law grounds (illegality, irrationality, procedural impropriety) subject to justiciability based on subject matter. Revolutionary extension of judicial review. R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5: Prerogative cannot trigger Article 50 as it would remove statutory rights under ECA 1972; fundamental constitutional change requires Parliament. Reinforces parliamentary sovereignty. R (Miller) v The Prime Minister [2019] UKSC 41: Prorogation advice unlawful as it frustrated Parliament's constitutional functions without justification. Courts enforce unwritten constitutional principles limiting executive power.

Courts first establish whether claimed prerogative power exists and define its scope. Then assess: (1) Does statute occupy the field? If yes, prerogative in abeyance—follow statute. (2) Is the power's exercise justiciable? Apply GCHQ subject-matter test but note Miller No 2 narrowed non-justiciable zone—now ask whether legal standards exist. (3) Would exercise remove/diminish statutory rights? If yes, unlawful without Parliament (Miller No 1). (4) Does exercise frustrate constitutional principles (sovereignty, accountability)? If yes, unlawful (Miller No 2). Common triggers: government attempting treaty action affecting domestic rights; use of Orders in Council; dissolution/prorogation; military deployment; honours. Key test post-Miller: significant constitutional change requires Parliament.

Confusing the two Miller cases—No 1 concerns Article 50/statutory rights; No 2 concerns prorogation/parliamentary functions. Misunderstanding 'abeyance'—statute suspends, not abolishes, prerogative; may revive if statute repealed. Claiming all prerogative now reviewable—GCHQ preserved non-justiciable categories; Miller No 2 narrowed but didn't eliminate them. Ignoring dissents—three Justices in Miller No 1 argued Article 50 didn't legally change domestic law. Overstating Miller No 2—decision fact-specific to five-week prorogation frustrating Parliament, not all prorogations reviewable.