Prerogative power and statute covering the same ground (De Keyser principle, Miller)

In R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5, the majority restated the principle from Attorney General v De Keyser's Royal Hotel Ltd [1920] AC 508. Consistently with parliamentary sovereignty, a prerogative power, however well established, may be curtailed or abrogated by statute, either by express words or, more commonly, by necessary implication. Because the prerogative is residual, it is displaced in a field which becomes occupied by a corresponding power conferred or regulated by statute. In De Keyser itself the Crown could not requisition a hotel under the prerogative to avoid a statutory compensation scheme. Here the 2024 Act regulates exactly what the Secretary of State has done. The prerogative is therefore displaced, and she must act under the statutory power, with compensation assessed under the statutory scheme. Lowri can challenge the decision by judicial review.

Why B is wrong: Miller confirms that abrogation may be by necessary implication; a statute covering the same ground displaces the prerogative without express words.

Why C is wrong: Parliamentary sovereignty means statute prevails over the prerogative, not the other way round.

Why D is wrong: The existence and extent of a prerogative power, and whether it has been displaced by statute, are questions of law for the courts.

Why E is wrong: No parliamentary resolution is needed; the statute itself displaces the prerogative in the field it occupies.