Royal prerogative and Miller (Nos 1 and 2)

The royal prerogative is the residue of legal authority left to the Crown and exercised in practice by ministers. Its constitutional significance lies not in monarchical romance, but in the allocation of public power between Parliament, the executive and the courts. In a modern constitution built on parliamentary sovereignty and responsible government, prerogative powers are executive powers recognised by the common law, limited by statute, and subject in appropriate cases to judicial control.

This topic is central to The Individual and the State because it tests the legal conditions under which government may act without fresh statutory authority. It also links the earlier Durham weeks. Week 1 supplied the idea of an uncodified constitution constituted by statutes, common law, conventions and political practices. Week 2 explained parliamentary sovereignty. Week 3 introduced constitutional statutes and the resistance of fundamental statutes to casual displacement. Week 4 considered the rule of law as a discipline on public power. Week 5 considered separation of powers. The prerogative sits at the intersection of all five: an ancient common law source of executive power disciplined by parliamentary supremacy, legality and judicial review.

The two Miller decisions are not isolated Brexit cases. Miller (No 1) concerned whether ministers could use the treaty prerogative to give notice under Article 50 TEU without an Act of Parliament. The Supreme Court held that they could not, because notification would inevitably alter domestic law rights created by the European Communities Act 1972 and the wider statutory scheme. The point was not that treaties are generally non-justiciable. It was that the executive cannot, through prerogative action on the international plane, change domestic law or frustrate statute.

Miller (No 2), joined with Cherry, concerned whether the Prime Minister's advice to prorogue Parliament for an unusually long period in autumn 2019 was reviewable and lawful. The Supreme Court held that it was justiciable and unlawful because it had the effect of frustrating or preventing, without reasonable justification, Parliament's ability to carry out its constitutional functions. The reasoning drew on parliamentary sovereignty and parliamentary accountability, rather than on ordinary Wednesbury review.

For Durham assessment, the strongest answers avoid two errors. First, do not treat the prerogative as a mysterious political zone beyond law. The courts have long determined whether a prerogative exists, what its legal limits are, and whether statute has displaced it. Secondly, do not treat Miller (No 2) as ordinary administrative law in constitutional clothing. Its distinctiveness lies in the court's formulation of a constitutional standard for a prerogative power affecting the institutional conditions of parliamentary government.

The prerogative developed from the Crown's historical authority as the organising centre of government. Its modern form is the legal remainder of that authority after centuries of statutory regulation, parliamentary control and judicial limitation. Dicey's well-known description of the prerogative as the residue of discretionary or arbitrary authority legally left in the hands of the Crown remains useful if read carefully. Residue does not mean immunity. It means powers not conferred by statute but recognised by common law.

The early constitutional settlement was forged through conflict between Crown and Parliament. The Case of Proclamations established the classic proposition that the Crown cannot by proclamation change the law or create new offences. The Bill of Rights 1688 entrenched the illegality of suspending laws by royal authority without parliamentary consent. These principles matter because the prerogative is lawful only within the limits allowed by law. The executive may possess powers over foreign affairs, defence, passports, honours, mercy, the organisation of the civil service and the conduct of diplomacy, but those powers cannot be used to override statute or alter domestic legal rights.

In the nineteenth and twentieth centuries, responsible government transferred practical control of Crown powers to ministers accountable to Parliament. The legal fiction of Crown power remained; the political reality became ministerial advice and ministerial responsibility. This is why modern cases speak of prerogative powers being exercised by ministers. The individual citizen's concern is therefore not monarchical privilege but governmental legality. If ministers may invoke an unwritten executive power, what prevents that power from bypassing Parliament?

The twentieth-century cases supplied the main doctrinal answers. Attorney General v De Keyser's Royal Hotel Ltd established that where statute occupies the field, ministers must use the statute and accept the statutory conditions, including compensation. Laker Airways and Fire Brigades Union developed the idea that the prerogative cannot be used to frustrate the policy or operation of legislation. CCSU confirmed that the source of power is not decisive for judicial review: prerogative powers may be reviewable, although some subject matters remain unsuitable for judicial determination.

Brexit brought these principles into sharp relief. Article 50 notification was formally an act in international law. Ordinarily, making and unmaking treaties falls within the foreign affairs prerogative. But EU membership was domestically unusual. The European Communities Act 1972 created a conduit through which EU law became a source of domestic law and domestic rights. The legal question was whether ministers could switch off that conduit by prerogative action. Miller (No 1) answered no.

The prorogation litigation arose from a different pressure point. Prorogation is a prerogative act bringing a parliamentary session to an end. It is not dissolution, and it does not abolish Parliament, but it prevents Parliament from sitting, debating, legislating and scrutinising ministers during the period of prorogation. In 2019, the Supreme Court had to decide whether the courts could impose legal limits on advice to prorogue where parliamentary government itself was impeded. Miller (No 2) answered yes.

The historical arc is therefore coherent. The prerogative began as Crown authority; it became ministerial executive power; it is now a legally limited category of public power. Miller did not invent that proposition. It applied it at moments when executive action threatened statutory rights and the functioning of Parliament.

1. The prerogative is a common law source of executive power. It is not a reserve of uncontrolled discretion. Courts determine whether a prerogative power exists and what its legal boundaries are. This is orthodox since the Case of Proclamations and is essential to the rule of law. If ministers claim power to act, they must identify a legal source. That source may be statute, common law capacity, or prerogative. The label prerogative does not end the inquiry.

1. The prerogative cannot create, amend or repeal domestic law. This is the central proposition behind both the Bill of Rights settlement and Miller (No 1). Ministers may conclude a treaty on the international plane, but they cannot by treaty alter domestic law unless Parliament has made domestic provision. The dualist structure of the United Kingdom constitution is therefore crucial. International obligations do not automatically become domestic law. Conversely, an international act may be legally constrained where its inevitable domestic consequence is to remove statutory rights or alter a statutory scheme.

1. Statute prevails over prerogative. De Keyser's principle is often stated as displacement or abeyance. Where Parliament has legislated in a field previously governed by prerogative, ministers cannot sidestep the statute by invoking the older prerogative. The stronger analysis is not that the prerogative is destroyed for all time, but that it cannot be used inconsistently with the statutory regime while that regime is in force. This gives practical force to parliamentary sovereignty: Parliament may regulate the executive, impose procedures, create rights, require compensation, or remove powers.

1. The prerogative cannot frustrate legislation. The cases go beyond simple conflict. Fire Brigades Union held that ministers could not use prerogative powers to introduce a non-statutory criminal injuries scheme inconsistent with a statutory scheme enacted but not yet brought into force. Miller (No 1) is best read as an application of the same family of reasoning. If the European Communities Act 1972 created a scheme under which EU law operated domestically, the executive could not use Article 50 notification to empty that scheme of practical content without Parliament.

The case law develops along three lines: the existence of prerogative power, its subordination to statute, and its amenability to review.

The Case of Proclamations is the beginning of the orthodox account. The Crown could not create offences or change the law by proclamation. Its importance is not merely historical. It establishes the judicial function of identifying legal limits on executive power. The courts, not ministers, decide the existence and scope of the prerogative.

De Keyser's Royal Hotel is the leading authority on statutory displacement. During wartime, the government requisitioned property. A statutory scheme provided for compensation; the Crown sought to rely on prerogative power instead. The House of Lords held that where statute covers the ground, the executive must act under statute. The case is indispensable in exam answers because it supplies the bridge between parliamentary sovereignty and executive power.

Laker Airways and Fire Brigades Union show that the principle is not confined to direct inconsistency. In Laker, the Crown could not use treaty and prerogative powers to undermine statutory licensing rights. In Fire Brigades Union, ministers could not use the prerogative to introduce an alternative scheme that frustrated a statutory scheme enacted by Parliament. These cases anticipate the reasoning in Miller (No 1): the executive may not use non-statutory power to defeat Parliament's legal design.

CCSU is the classic reviewability case. The prerogative source of a power does not automatically immunise it from review. However, reviewability may be limited by subject matter. National security, foreign affairs and high policy may require judicial restraint. This distinction helps explain why Miller (No 1) and Miller (No 2) were justiciable: both involved legal limits on constitutional power, not the merits of diplomacy or policy.

Miller (No 1) held that Article 50 notification required statutory authority. The majority reasoned that withdrawal would remove a source of domestic law and domestic rights created by the 1972 Act. The treaty prerogative could not be used to produce that domestic legal change. The dissenters, especially Lord Reed, viewed the 1972 Act as conditional on the continuing existence of EU treaties and therefore not a limit on the treaty prerogative. That disagreement is doctrinally important.

Miller (No 2) held that advice to prorogue was justiciable and unlawful. The court formulated a constitutional limit grounded in parliamentary sovereignty and accountability. The remedy was equally striking: the prorogation was null, so Parliament had not been prorogued. The Speaker and Lord Speaker could resume proceedings. The case is a leading example of constitutional principle generating a legal standard for review of prerogative action.

See practice questions section below.

See further reading section below.