Prerogative powers - Definition and scope of prerogative pow...

Learning Outcomes

This article explains the definition, scope, limits, and judicial review of prerogative powers within the UK constitution, including:

• The legal nature of prerogative powers, their historical development, and their status as residual Crown powers.
• The main categories of prerogative powers in foreign affairs, defence, domestic governance, and justice, with typical exam-ready examples.
• The place of prerogative powers among statutes, common law, and constitutional conventions as sources of constitutional authority.
• The relationship between prerogative powers, parliamentary sovereignty, and the rule of law, including how statute can displace or regulate them.
• Clear distinctions between prerogative authority and overlapping statutory or judicially recognised powers, with emphasis on statutory supremacy.
• Leading cases on prerogative power, such as De Keyser, GCHQ, and the Miller decisions, and the principles they establish.
• The criteria for justiciability, non-justiciable areas of high policy, and how courts apply public law grounds to prerogative decisions.
• Practical consequences of unlawful or improper exercises of prerogative powers, including available judicial remedies and procedural routes.
• The continuing constitutional significance of prerogative powers, modern statutory and political constraints, and their relevance to SQE1 problem questions.

SQE1 Syllabus

For SQE1, you are required to understand prerogative powers within the UK constitution, with a focus on the following syllabus points:

• Definition and legal basis of prerogative powers in the UK constitution, including historical development.
• Main categories of prerogative powers with current and practical examples.
• The relationship between prerogative powers, statutory authority, and case law.
• The constitutional importance of prerogative powers and how they are constrained by parliamentary supremacy, the rule of law, and judicial review.
• How prerogative powers interact with constitutional conventions and political accountability.
• Circumstances and doctrinal basis for judicial review of prerogative powers, with clear distinctions between justiciable and non-justiciable prerogative powers.
• The effect of statute on the existence, exercise, and revival of prerogative powers.

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. What is the legal source of prerogative powers in the UK constitution?
2. Can a prerogative power be exercised in an area where Parliament has legislated?
3. Name two main categories of prerogative powers and give an example of each.
4. Are all prerogative powers subject to judicial review? Explain your answer.
5. What principle was established in Attorney General v De Keyser’s Royal Hotel Ltd [1920]?

Introduction

Prerogative powers are a central aspect of the UK’s uncodified constitution, representing a class of constitutional powers originally exercised by the monarch but now almost exclusively in the hands of government ministers. Their existence and use reflect the balance between executive action, parliamentary supremacy, and judicial oversight in the UK’s constitutional arrangements. Understanding their nature, limits, and review mechanisms is essential for constitutional analysis and effective legal practice in public law contexts.

Definition and Legal Basis

Prerogative powers are those legal powers and privileges that remain vested in the Crown by customary law and are recognised by the courts. They are not creatures of statute but form part of the UK’s common law constitutional inheritance. Historically, these powers were exercised at the personal discretion of the monarch; today, constitutional conventions require that they are exercised solely on the advice of government ministers.

Key Term: prerogative powers
Prerogative powers are residual powers and privileges of the Crown, recognised under the common law, and now in practice exercised by ministers in areas not otherwise regulated or preempted by statute.

The critical feature of prerogative powers is their residual character—they apply only where Parliament has not “occupied the field” with statutory authority. Once Parliament legislates in an area formerly governed by the prerogative, the prerogative is either displaced or remains dormant.

Key Term: residual powers
Residual powers refer to the executive's authority that remains where no statutory regulation exists. Such powers are lost or suspended when Parliament enacts legislation covering the relevant field.

The courts have consistently ruled that the scope and existence of prerogative powers are a matter for the judiciary, not the government. The famous Case of Proclamations (1611) and BBC v Johns [1965] established that no new prerogative powers can be created, and that any alleged prerogative can only be invoked if it is supported by historic legal authority.

Scope and Main Categories

Prerogative powers are finite and cannot be extended by the executive. Their scope reflects the historical allocation of governmental functions prior to modern legislation. Today, the main categories of prerogative powers, as recognised by case law and government review, include:

Foreign Affairs and Defence

• The conduct of foreign relations and recognition of foreign states.
• Making, ratifying, and withdrawing from international treaties (though Parliament must now approve ratifications under the Constitutional Reform and Governance Act 2010).
• Deployment and command of the armed forces, including declarations of war and peace.
• Appointment and receipt of diplomats.

Domestic Governance

• Summoning, proroguing, and (historically) dissolving Parliament (the latter has been regulated by legislation, e.g. by the Dissolution and Calling of Parliament Act 2022).
• Appointment and dismissal of ministers and other senior public officials.
• Granting of honours and titles.
• Issuing and withdrawing passports (subject to statutory and judicial oversight).

Justice System and Royal Mercy

• Granting reprieves, pardons (the “prerogative of mercy”), or commutations of sentences.
• Issuing Orders in Council under the prerogative (in limited circumstances).
• Creation and management of certain types of royal charter.

Miscellaneous

• Control of the civil service—previously prerogative, now largely statutory under the Constitutional Reform and Governance Act 2010.
• Regulation of particular royal rights, such as ownership of certain wildlife (e.g. swans, sturgeon), precious metals, and the minting of coinage.

Key Term: prerogative of mercy
The discretion of the Crown, exercised by government ministers, to offer pardon or reduce a sentence, typically for considerations of justice, equity, or public policy.

These powers are not static, and their operation is often shaped by statute or evolving constitutional convention. For example, the practice of seeking parliamentary approval before committing armed forces to conflict, though not legally mandatory, has become a significant constitutional convention.

Constitutional Significance and Limitations

Prerogative powers allow the executive to operate flexibly and efficiently in certain governmental functions without awaiting specific statutory authority, often in matters where legislative action would be impracticable or too slow. Nevertheless, their continued existence and legitimate use are circumscribed by important constitutional principles:

Parliamentary Sovereignty

One of the cornerstones of the UK constitution is the sovereignty of Parliament. Prerogative powers must yield to statute. If Parliament legislates in an area previously governed by the prerogative, the statutory provisions are supreme, and the prerogative is explicitly or implicitly abrogated, suspended, or placed in abeyance while the statute is in force.

Key Term: statutory supremacy
Statutory supremacy is the doctrine that statutory law enacted by Parliament can override, limit, or extinguish any existing prerogative power.

This principle was clearly stated in Attorney General v De Keyser’s Royal Hotel Ltd [1920] AC 508, where the House of Lords held that the government could not use the prerogative to avoid paying statutory compensation. Where a statutory regime exists, the executive may not rely instead on the prerogative, and the prerogative is displaced for as long as the statute remains in effect.

Subsequent cases such as R v Secretary of State for the Home Department, ex parte Fire Brigades Union [1995] confirmed that the executive could not sidestep (or create alternative to) a statutory scheme by relying on the prerogative.

Rule of Law

Another key constitutional pillar is the rule of law, which requires that the government act within legal limits and be subject to judicial scrutiny. This demonstrates the importance of judicial oversight, particularly as regards the exercise and scope of prerogative powers. The rule of law restricts arbitrary or excessive executive action and underpins judicial review of prerogative power where justiciable.

Key Term: judicial review of prerogative
Judicial review of prerogative denotes the process by which the courts determine the lawfulness of the exercise (or purported exercise) of prerogative powers, ensuring such acts are within their proper scope and comply with legal standards.

The courts have also clarified that the “rule of law” includes the principle of equality before the law, meaning that even government ministers exercising prerogative power are potentially subject to court action, as affirmed in M v Home Office [1994] 1 AC 377.

Relationship with Statute

While prerogative powers may exist in addition to statutory powers, the executive is obliged to use statutory powers where available. The courts will not allow the government to revive a prerogative power dormant due to statutory intervention unless the relevant statute is expressly repealed (and the prerogative is not abrogated by that repeal).

Prerogative and statutory powers may operate side by side if their scopes do not fully overlap—see R v Secretary of State for the Home Department, ex parte Northumbria Police Authority [1989], where both a statutory provision and a parallel prerogative co-existed in so far as the statute did not expressly or by necessary implication exclude the prerogative.

Constitutional Conventions

While conventions do not have the force of law, they can regulate the exercise of prerogative powers and form an important component of the political constitution. For example, the modern convention is that the Crown acts only on ministerial advice, and ministers are, by convention, collectively and individually responsible (and thus accountable) to Parliament for prerogative acts. Importantly, in some areas, such as military action, there is a developing convention that Parliament should be consulted, even where this is not legally required.

Judicial Review of Prerogative Powers

Historically, the courts generally considered prerogative powers to be outside judicial oversight, aligning with the doctrine of non-justiciability for certain categories of executive action—particularly those involving matters of “high policy” (e.g. foreign affairs, defence, dissolution of Parliament). However, this approach was reappraised in Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374 (the GCHQ case). The House of Lords held that the courts could, in principle, review the exercise of prerogative powers, subject to their nature and context.

Key Term: non-justiciable powers
Non-justiciable powers are prerogative powers which the courts decline to review, usually because they concern matters of high policy, such as national security, defence of the realm, treaty-making, dissolution of Parliament, or the grant of honours.

The GCHQ case affirmed that the justiciability of prerogative power depends on the subject matter, not its origin. While areas touching on national security, diplomatic relations, or the deployment of armed forces remain typically non-justiciable, exercises of prerogative affecting individual rights, legitimate expectations, or administrative fairness can be scrutinised by the courts and may be subject to judicial remedies.

Since GCHQ, the courts have further extended their willingness to review prerogative powers in relevant contexts. For example, in R (Miller) v The Prime Minister [2019] UKSC 41, the Supreme Court held that the Prime Minister’s advice to prorogue Parliament was reviewable and, in that case, unconstitutional.

Grounds of judicial review applicable to prerogative action are generally those applied to statutory action:

• Illegality: exercise of the power outside its lawful scope,
• Irrationality (Wednesbury unreasonableness): the decision could not reasonably have been made by any rational government official in that position,
• Procedural impropriety: failure to comply with required procedures (including procedural fairness or natural justice).

Worked Example 1.1

A minister refuses a UK national a passport, citing the Crown’s prerogative power over passport issuance, without providing a reason. The individual believes the refusal is simply arbitrary and seeks judicial review.

Answer:
The courts recognise that the issuance of passports under the prerogative is reviewable. Where a refusal affects individual rights, and no satisfactory reason is given, the courts can assess whether there has been an abuse of discretion or irrationality. Unless the refusal relates to non-justiciable grounds such as national security (where evidence would be needed), judicial review is available.

Worked Example 1.2

Following parliamentary legislation establishing a statutory scheme for compensation for property requisitioned in an emergency, the government attempts to rely on the prerogative to avoid paying compensation under the new scheme.

Answer:
The government cannot use prerogative power where a statutory scheme covers the relevant subject matter. The statute overrides the prerogative, and the government must comply with its terms; any attempt to sidestep the statute would be invalid.

Worked Example 1.3

A group of campaigners challenge a government decision to remove British citizenship from an individual using a statutory power and, subsequently, the refusal to grant re-entry under the Crown’s prerogative.

Answer:
Where statutory powers are engaged, the government must use those, not the prerogative. However, if an individual is no longer a UK citizen by statute, the Crown’s residual discretion under the prerogative (e.g. to issue a passport or grant entry clearance) may apply. The use of the prerogative can be judicially reviewed if it impacts legal rights.

Limits and Recent Developments

Legal and political developments in the late twentieth and early twenty-first centuries have resulted in a clearer understanding of both the sources and the boundaries of prerogative power:

• The government cannot create new prerogative powers (see BBC v Johns [1965]), and can only rely on powers that the courts recognise as existing.
• Statutes may expressly abolish, regulate, or leave dormant the prerogative (but not revive it unless so specified).
• With the Human Rights Act 1998, if the use of prerogative power breaches convention rights, courts may make a declaration of incompatibility (see, e.g., Orders in Council made under the prerogative, such as those affecting overseas territories).
• Political and constitutional conventions have increasingly called for major uses of prerogative (e.g. military action, treaty ratification, prorogation of Parliament) to be subject to parliamentary debate and approval.

Modern case law sets out clear boundaries to the use and review of prerogative powers:

• R (Miller) v Secretary of State for Exiting the European Union [2017]: The government could not use the prerogative to trigger Article 50 TEU and withdraw from the EU without Parliament’s express authorisation by legislation, because the European Communities Act 1972 conferred rights on individuals that only Parliament could remove.

• R (Miller) v The Prime Minister [2019]: The Supreme Court found the Prime Minister’s advice to prorogue Parliament was justiciable and unlawful, as it had the effect of frustrating Parliament without reasonable justification, undermining parliamentary sovereignty.

• R v Secretary of State for the Home Department, ex parte Fire Brigades Union [1995]: Statutory compensation scheme for victims of crime took precedence over prerogative-based schemes.

• R v Secretary of State for Foreign and Commonwealth Affairs, ex parte Everett [1989]: The exercise of the prerogative to issue passports was reviewable by the courts when used in a way that directly affected individuals’ rights.

Key Term: justiciability
Justiciability refers to whether an issue is suitable for court adjudication. In the context of prerogative powers, it distinguishes between those exercises of the prerogative that are susceptible to legal review (justiciable) and those that remain matters of high policy or politics (non-justiciable).

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Prerogative powers are discretionary executive powers recognised by the common law, now exercised by ministers in practice on behalf of the Crown.
• Their scope is residual, limited to areas not covered by statute, and they diminish as Parliament legislates.
• Statutory authority takes precedence over prerogative power; Parliament may abolish or suspend prerogative power by legislation.
• The courts may review the exercise of prerogative powers, except in cases where the subject matter is non-justiciable due to its nature (e.g. foreign policy or national security).
• Prerogative powers can be indirectly regulated or influenced by constitutional conventions, and ministers are politically accountable to Parliament for their use.
• Judicial review applies to prerogative powers using regular public law grounds—illegality, irrationality, procedural impropriety—subject to limits on justiciability.
• No new prerogative powers can be created; their existence and extent are defined and policed by the courts.
• The impact of the Human Rights Act 1998 enables courts to issue declarations of incompatibility if the exercise of a prerogative power contravenes Convention rights, although Parliament retains the right to uphold or amend legislation.
• The ongoing legitimacy of prerogative powers is sustained by the combined operation of statute, judicial oversight, and constitutional convention.

Key Terms and Concepts

• prerogative powers
• residual powers
• prerogative of mercy
• statutory supremacy
• judicial review of prerogative
• justiciability
• non-justiciable powers