The Royal Prerogative: Executive Powers, Constitutional Limits, and Judicial Review

The Royal Prerogative: Executive Powers, Constitutional Limits, and Judicial Review

Introduction

The royal prerogative is one of the most distinctive features of the United Kingdom’s constitutional system. It represents a body of powers historically associated with the Crown that continues to form part of the legal authority exercised by the modern state. Although these powers originated in the personal authority of the monarch, most are now exercised by ministers and other public authorities in accordance with established constitutional arrangements.

The royal prerogative is particularly important in areas such as foreign affairs, national defence, the appointment of ministers, the granting of certain honours and the formal summoning and prorogation of Parliament. However, the precise scope of each power depends on its historical development, applicable legislation, common law principles and constitutional practice.

The subject raises a fundamental question about the relationship between historical authority and modern constitutional government. How can powers originating in royal authority remain legally valid within a system based on parliamentary sovereignty, democratic accountability and the rule of law?

The answer lies in the transformation of the British constitution. The monarch remains the formal source through which certain prerogative powers are exercised, but the modern constitutional system generally requires the monarch to act on ministerial advice. Ministers, in turn, are accountable to Parliament and must exercise their powers within the limits imposed by law.

The royal prerogative is therefore not an unrestricted personal authority belonging to the sovereign. It is a legally recognised category of executive power whose existence and limits are determined by constitutional law.

This distinction became especially significant in two landmark Supreme Court cases. In R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5, the Court considered whether ministers could use prerogative powers to notify the European Union of the UK’s intention to withdraw without prior parliamentary authorisation. In R (Miller) v The Prime Minister; Cherry v Advocate General for Scotland [2019] UKSC 41, the Court examined the legal limits of the power to prorogue Parliament.

Both cases demonstrate that executive authority cannot be assessed solely by identifying its historical source. Its lawful exercise must also be considered in relation to legislation, constitutional principles and the rights and responsibilities of other institutions.

The relevant judgments are available from the official website of the Supreme Court of the United Kingdom. The House of Commons Library’s briefing on the royal prerogative and ministerial advice, published in August 2025, also provides a detailed account of the modern legal and constitutional position.

This article examines the meaning and historical development of the royal prerogative, its principal applications, its relationship with parliamentary sovereignty, the circumstances in which courts may review its exercise, and its continuing significance for constitutional government in the United Kingdom and the legal system of England and Wales.

Facts About the Royal Prerogative

The royal prerogative is a body of powers recognised by the common law as belonging historically to the Crown. In modern practice, many of these powers are exercised by ministers on behalf of the Crown rather than by the monarch personally.

The prerogative is sometimes described as the residue of the Crown’s historical legal authority that remains after powers have been removed, restricted, replaced or regulated by legislation and constitutional development.

It is not a single statutory power. Its scope consists of individual powers that have developed over time, and the legal boundaries of each must be considered separately.

Prerogative powers are commonly associated with the conduct of foreign affairs, aspects of national defence, certain appointments, the granting of honours and the formal processes through which Parliament is summoned or prorogued. The precise legal arrangements differ according to the power concerned, and some areas traditionally associated with the prerogative have been substantially regulated by statute.

The following principles are central to understanding the doctrine.

First, the royal prerogative is a legal concept, not simply a description of royal tradition. A claimed prerogative power must have a recognised legal basis. Ministers cannot invent a new prerogative merely because they consider a particular action desirable.

Second, prerogative powers cannot ordinarily be used to change domestic statute law or common law. Where legislation regulates an area, the executive must comply with the statutory framework. A prerogative power cannot be used to circumvent an Act of Parliament or frustrate its purpose.

Third, prerogative powers may be subject to judicial review. Courts can determine whether a power exists, establish its legal limits and examine whether its exercise is legally permissible. Whether a particular exercise is reviewable depends on the nature of the power, the legal issues raised and the applicable constitutional principles.

Fourth, the monarch generally acts on ministerial advice in the exercise of prerogative powers under modern constitutional conventions. Ministers who provide such advice bear political responsibility for it and may be required to account to Parliament.

Fifth, the royal prerogative must be distinguished from statutory powers. A statutory power derives from legislation and is governed by the terms of the relevant Act. A prerogative power derives from the common law and exists within the limits established by the legal system.

Finally, the royal prerogative operates within the wider constitutional structure of the United Kingdom. Its exercise may involve UK-wide responsibilities or matters relating to particular jurisdictions, depending on the subject and applicable constitutional arrangements.

1. What Is the Royal Prerogative?

The royal prerogative refers to certain powers recognised by the common law as belonging to the Crown by virtue of its constitutional position. Historically, these powers were associated with the monarch’s authority to govern, conduct foreign relations, maintain armed forces, appoint officials and perform other functions of the state.

The modern constitutional system has transformed the way these powers operate. The monarch generally exercises them in accordance with ministerial advice, while ministers exercise executive responsibilities within the applicable legal framework.

The distinction between the historical holder of a power and the person who exercises it in practice is fundamental. The Crown remains the formal constitutional source of many prerogative powers, but political decision-making and responsibility ordinarily rest with the Government.

For example, the formal power to appoint the Prime Minister belongs to the monarch. In practice, the appointment follows constitutional conventions concerning who is able to command the confidence of the House of Commons. The monarch is not expected to select a Prime Minister according to personal political preference.

Similarly, the Crown possesses prerogative powers connected with the conduct of foreign affairs, but the decisions associated with their exercise are generally made by ministers and are subject to relevant legal constraints.

The royal prerogative must therefore be understood as part of a constitutional system in which historical authority has been adapted to modern parliamentary government.

1.1 The difference between prerogative and statutory powers

A statutory power is created or conferred by legislation. Its existence, scope and conditions are determined by the relevant Act and the legal principles governing its interpretation.

A prerogative power, by contrast, is recognised by the common law rather than created by a specific statutory provision.

This difference matters because the source of a power influences how its limits are identified. When a minister exercises a statutory power, the starting point is the legislation conferring that authority. When a minister relies on the royal prerogative, the question is whether the claimed power exists at common law and, if so, what its legal boundaries are.

The distinction does not mean that prerogative powers are inherently more extensive than statutory powers. A statutory scheme may confer broad authority, while a prerogative power may be narrow or subject to significant restrictions.

Nor does the prerogative provide an alternative route through which ministers may disregard legislation. If Parliament has regulated a particular subject, the executive cannot ordinarily rely on the prerogative to evade the statutory framework.

The Supreme Court confirmed this principle in Miller [2017] UKSC 5. The Government could not use prerogative authority to initiate a process that would inevitably result in changes to domestic law and the removal of statutory rights created through legislation without the necessary parliamentary authorisation.

The official judgment is available at Miller [2017] UKSC 5.

1.2 Is the royal prerogative the personal property of the monarch?

No. Although the prerogative originated in royal authority, it is misleading to understand it as a collection of personal privileges that the monarch may exercise according to individual preference.

The modern constitutional system distinguishes the formal authority of the Crown from the political responsibilities of the Government.

The monarch generally acts on ministerial advice in the exercise of prerogative powers. The Government is responsible for determining policy within the relevant legal framework, while ministers are accountable to Parliament for their decisions.

This arrangement reflects the development of constitutional monarchy. The sovereign retains an important formal role, but political authority is exercised through institutions operating under constitutional conventions and legal constraints.

There may be exceptional circumstances in which constitutional questions arise about the advice given to the monarch or the precise scope of a particular royal function. Such matters must be considered according to the applicable legal and constitutional rules rather than assumptions that the monarch possesses unrestricted discretion.

The royal prerogative is therefore best understood as a historical source of public power that has been incorporated into the modern constitutional system.

2. Historical Development of the Royal Prerogative

The history of the royal prerogative reflects the transformation of the English monarchy from a system in which royal authority was central to government into a constitutional monarchy operating through parliamentary institutions.

In medieval England, the Crown exercised extensive authority over administration, justice, foreign relations and the maintenance of public order. The precise boundaries of royal power were shaped by custom, political circumstances and the developing common law.

Over time, conflicts between the Crown and Parliament contributed to the establishment of legal and constitutional limits on royal authority.

2.1 The medieval Crown and the development of legal limits

The medieval monarch exercised powers that would now be distributed across several government departments and public institutions. Royal authority included functions associated with the administration of justice, the conduct of war, diplomatic relations and the appointment of officials.

However, royal power did not develop in a legal vacuum. Custom, established practices and the common law gradually shaped the boundaries of the Crown’s authority.

Magna Carta, originally issued in 1215 and subsequently reissued in revised forms, became an important historical symbol of the proposition that royal authority could be subject to legal constraints.

It did not establish a modern separation of powers or eliminate royal prerogative. Its constitutional significance lies partly in the longer history of arguments that the monarch was not simply above the law.

Over subsequent centuries, the relationship between the Crown and Parliament changed substantially. Parliament became increasingly important in taxation, legislation and the supervision of government.

2.2 The Case of Proclamations 1611

An important early judicial statement about the limits of royal authority appears in the Case of Proclamations (1611).

The case arose during the reign of James I, when the Crown sought to regulate conduct through royal proclamations. The question concerned whether the King could use the prerogative to create legal restrictions without an appropriate basis in the existing law.

The court rejected the proposition that the monarch could create new prerogative powers simply by declaring them. Royal authority was limited by the law of the land.

The case is traditionally associated with the principle that the Crown possesses only those prerogative powers recognised by law.

Its continuing significance is considerable. It establishes that the existence and extent of royal authority are legal questions, not matters determined exclusively by the monarch’s assertion of power.

The principle also provides a foundation for judicial supervision of executive authority. If a minister claims to exercise a prerogative power, the legal system must be capable of determining whether that power exists and what restrictions apply to it.

2.3 The seventeenth-century constitutional conflicts

The constitutional conflicts of the seventeenth century further restricted the practical exercise of royal authority.

Disputes over taxation, religion, legislation and the relationship between the Crown and Parliament contributed to the English Civil Wars, the execution of Charles I in 1649, the subsequent republican period and the Restoration of the monarchy in 1660.

The Glorious Revolution of 1688 and the Bill of Rights 1689 established important constitutional limitations on royal authority and strengthened Parliament’s position.

The Bill of Rights addressed matters including the suspension of laws, taxation without parliamentary authority and the maintenance of a standing army in peacetime without parliamentary consent.

These developments did not abolish the royal prerogative. Instead, they contributed to a constitutional settlement in which royal powers increasingly operated within a framework of parliamentary authority and legal restraint.

The subsequent development of cabinet government and ministerial responsibility further transformed the relationship between the Crown and the executive.

2.4 The rise of ministerial government

As parliamentary government developed, political responsibility for executive decisions increasingly rested with ministers rather than the monarch personally.

The constitutional convention that the monarch ordinarily acts on ministerial advice became central to the operation of the modern system.

This development produced an important distinction between formal authority and practical responsibility. The Crown continued to provide the legal and constitutional framework through which certain powers were exercised, while ministers made the relevant political decisions.

The Prime Minister and Cabinet became responsible for directing government policy, and ministers became accountable to Parliament for the conduct of their departments.

The royal prerogative survived because the constitutional system did not replace every historical executive power with a statutory provision. Instead, some powers remained recognised at common law, while others were regulated, limited or replaced by legislation.

The modern prerogative is therefore a product of constitutional evolution rather than a complete survival of medieval royal government.

2.5 The modern constitutional settlement

Today, the royal prerogative operates alongside parliamentary sovereignty, the rule of law, judicial review and ministerial accountability.

Some powers remain important because they provide legal authority for executive functions that have not been comprehensively codified in legislation. Others have been significantly affected by statutory reform.

The Constitutional Reform and Governance Act 2010, for example, established a statutory framework governing the ratification of treaties, subject to its provisions and exceptions. This illustrates how areas traditionally associated with the prerogative may be brought within a legislative framework.

The official legislation is available at Constitutional Reform and Governance Act 2010.

The modern royal prerogative is consequently neither an unlimited survival of personal royal power nor an entirely obsolete historical concept. It remains a legally significant source of executive authority, but one that must operate within the contemporary constitution.

Constitutional Insight

The history of the royal prerogative illustrates a recurring constitutional transformation: powers once associated with the personal authority of a ruler can survive as legal institutions while their exercise becomes subject to public responsibility, parliamentary accountability and judicial scrutiny.

3. Principal Categories of Royal Prerogative Powers

The royal prerogative consists of distinct powers rather than one general authority to govern. Each power has its own history, scope and legal limitations.

The categories commonly associated with the prerogative include foreign affairs, national defence, certain appointments, honours, the summoning and prorogation of Parliament and aspects of the prerogative of mercy.

The following sections explain the principal areas in which these powers remain constitutionally significant.

3.1 Foreign affairs and international relations

The conduct of foreign affairs has historically been associated with the Crown. In modern practice, ministers generally exercise the relevant executive responsibilities.

These functions include diplomatic relations, negotiations with foreign states and aspects of treaty-making. However, the legal position must be considered in light of the statutory framework applicable to the particular matter.

Treaty-making illustrates the relationship between executive authority and parliamentary sovereignty.

The Government may negotiate and sign treaties in accordance with the relevant constitutional and international arrangements. The domestic legal consequences of those treaties are a separate question.

A treaty does not ordinarily change domestic law merely because the UK has entered into it. Where implementation requires a change in domestic law, the necessary legislative authority must be obtained.

The Constitutional Reform and Governance Act 2010 also establishes parliamentary procedures relating to treaty ratification, subject to the statutory framework and applicable exceptions.

The distinction between international action and domestic legal authority is essential. The Government may possess authority to negotiate an international agreement, but it cannot assume that every obligation in the agreement automatically becomes enforceable domestic law.

3.2 National defence and the armed forces

Prerogative powers have traditionally been associated with the deployment and administration of the armed forces and other aspects of national defence.

In modern government, these responsibilities are exercised through ministers and the relevant defence institutions. The legal framework may also include statutory powers, legislation governing the armed forces and other applicable legal obligations.

The existence of prerogative authority does not mean that every decision involving national security is beyond judicial scrutiny. Courts may consider whether a power exists and whether its exercise raises a legal question that can properly be determined through judicial proceedings.

However, the nature of defence and security decisions may affect the issues a court can realistically determine. Some matters involve operational assessments, confidential information or complex judgments that are not readily resolved through ordinary judicial procedures.

The constitutional distinction is between recognising the executive’s responsibility for defence policy and treating all executive action in this area as legally unlimited.

The royal prerogative does not provide a general exemption from the law.

3.3 Appointment of the Prime Minister and ministers

The monarch formally appoints the Prime Minister and other ministers according to the applicable constitutional arrangements.

The appointment of a Prime Minister is governed by constitutional conventions concerning the formation of a government capable of commanding the confidence of the House of Commons.

Following a general election, the monarch does not ordinarily choose a Prime Minister according to personal political preference. The appointment must reflect the constitutional position of the political parties and the person able to form a government with the necessary parliamentary support.

The appointment of other ministers similarly occurs through formal processes involving the Crown and the Prime Minister.

The distinction between formal appointment and political responsibility is important. Although the monarch performs the formal constitutional act, the composition and direction of the Government are primarily matters of political responsibility.

These arrangements illustrate the transformation of royal authority into a constitutional framework governed by parliamentary government and convention.

3.4 Summoning and proroguing Parliament

The Crown has prerogative powers associated with summoning and proroguing Parliament, although the legal and constitutional arrangements surrounding parliamentary sessions must be considered in detail.

Summoning Parliament brings the Houses together for a parliamentary session in accordance with the relevant constitutional arrangements.

Prorogation formally ends a parliamentary session. It differs from dissolution, which ends the Parliament itself and is associated with a general election.

Prorogation can have significant constitutional consequences because parliamentary proceedings cease during the period in which Parliament is prorogued, subject to the applicable legal framework.

The power became the subject of major constitutional litigation in 2019, when the Supreme Court considered whether the advice to prorogue Parliament for an extended period was lawful.

In Miller/Cherry [2019] UKSC 41, the Court held that the advice was unlawful because the prorogation had the effect of frustrating or preventing Parliament from carrying out its constitutional functions without reasonable justification.

The judgment is examined in detail later in this article.

3.5 The granting of honours

The Crown possesses prerogative powers associated with the granting of certain honours.

In modern practice, honours are generally awarded through established systems involving nominations, assessment and ministerial or other institutional procedures.

The formal role of the Crown does not mean that honours are distributed solely according to the monarch’s personal preferences. The relevant constitutional and administrative arrangements determine how nominations are considered and awards are made.

The granting of honours also illustrates a distinction between the legal existence of a prerogative power and the practical procedures through which it is exercised.

The fact that a power has historical royal origins does not mean that it operates without established conventions or administrative safeguards.

3.6 The prerogative of mercy

The prerogative of mercy is associated with the power to grant pardons or otherwise exercise certain forms of clemency.

Historically, this power reflected the Crown’s authority to show mercy in particular cases. In modern practice, decisions are generally taken through the relevant governmental arrangements and must be understood in the context of applicable law.

The precise scope and legal consequences of a pardon depend on the type of decision involved. A pardon should not be assumed to have the same effect as an acquittal, the reversal of a conviction or the removal of every legal consequence associated with an offence.

The prerogative of mercy is an example of a historical power that continues to have constitutional significance, but its exercise must be distinguished from ordinary judicial adjudication.

A court determines legal issues according to law. The prerogative of mercy concerns a different constitutional function, although questions about its legal limits and the lawfulness of particular decisions may arise before the courts.

4. The Royal Prerogative and Parliamentary Sovereignty

The relationship between the royal prerogative and parliamentary sovereignty is one of the most important features of the modern British constitution.

Parliamentary sovereignty concerns the legal authority of Parliament to enact and repeal primary legislation. The royal prerogative concerns certain executive powers recognised by the common law.

The two concepts can operate together, but prerogative authority cannot ordinarily be used to override legislation.

This distinction is essential because the executive must not be permitted to use historical powers to circumvent decisions made through the legislative process.

4.1 The principle that statute prevails

Where Parliament has legislated on a matter, the executive must comply with the applicable statutory framework.

The prerogative cannot ordinarily be used to change statute law or common law. Nor may ministers use it to frustrate the purpose of legislation.

The Supreme Court explained this principle in Miller [2017] UKSC 5. The case concerned the Government’s intention to notify the European Council under Article 50 of the Treaty on European Union, thereby beginning the process of the UK’s withdrawal from the EU.

The Government argued that it could give the notification through the royal prerogative, relying on the traditional executive authority associated with foreign affairs and treaty-making.

The Supreme Court rejected that argument. The European Communities Act 1972 had created a statutory framework through which EU law took effect domestically. Giving notification under Article 50 would inevitably lead to changes in domestic law and the loss of statutory rights when withdrawal took effect.

The executive could not use the prerogative to bring about that result without parliamentary authorisation.

The judgment did not establish that every decision relating to international relations requires a new Act of Parliament. Rather, it confirmed that prerogative powers cannot be used to alter domestic law or remove statutory rights contrary to the constitutional principle that such changes require lawful legislative authority.

4.2 Why the Government cannot rely on the prerogative to bypass Parliament

The Government and Parliament are distinct constitutional institutions.

The Government may exercise executive powers and propose legislation, but it cannot treat the prerogative as a general alternative to parliamentary legislation whenever a policy objective would be difficult to achieve through Parliament.

If ministers could use prerogative powers to override statutory restrictions, the authority of Parliament to make law would be weakened.

The constitutional principle is that executive power must remain consistent with the law established by Parliament. Where legislation has prescribed the legal framework for a particular subject, ministers cannot ordinarily evade that framework by invoking a historical executive power.

This principle applies even where the Government believes that its proposed action would be politically desirable or administratively convenient.

4.3 Can Parliament abolish or restrict a prerogative power?

Parliament may legislate to regulate, restrict or remove prerogative powers.

An Act of Parliament may replace a prerogative arrangement with a statutory scheme, establish conditions for its exercise or provide that a particular power is no longer available in its previous form.

The effect of legislation depends on its wording and the relevant legal principles. Not every statute affecting a subject automatically abolishes every associated prerogative power, and the relationship between statute and prerogative may require careful interpretation.

Nevertheless, the central principle remains that prerogative powers cannot override an inconsistent statutory rule.

This gives Parliament an important constitutional role in determining the legal framework within which the executive operates.

4.4 Parliamentary sovereignty and constitutional accountability

The royal prerogative demonstrates why parliamentary sovereignty must be understood as more than the formal power to enact legislation.

The constitutional framework also requires a distinction between the authority to make law and the authority to administer it.

Parliament establishes legal rules. Ministers exercise executive powers within the applicable framework. Courts determine disputes concerning the existence and limits of those powers.

The interaction between these institutions helps prevent the executive from treating its political objectives as an independent source of legal authority.

Constitutional Insight

The royal prerogative illustrates the difference between possessing power and possessing the legal authority to exercise it in a particular way. A constitutional system must recognise executive capacity without allowing that capacity to displace the law.

5. The Royal Prerogative and the Rule of Law

The rule of law requires public authorities to exercise their powers according to law. The royal prerogative is subject to this principle.

Although prerogative powers do not derive from a specific statutory provision in the same way as statutory powers, they remain part of the legal system. Their existence and limits are determined by the common law, and their exercise must comply with applicable legislation and constitutional principles.

The fact that a decision is made under the prerogative does not automatically place it beyond the reach of the courts.

5.1 The principle of legality

The principle of legality requires public authorities to act within the legal powers available to them.

For statutory powers, the relevant authority must be found in legislation. For prerogative powers, the authority must be recognised by the common law and exercised within its lawful boundaries.

This distinction prevents ministers from treating the prerogative as an undefined reservoir of executive discretion.

A minister cannot establish the existence of a prerogative power merely by asserting that the matter falls within government responsibility. The relevant legal question is whether the power exists and whether the proposed action falls within its scope.

The Case of Proclamations established an early foundation for this principle by rejecting the idea that the Crown could create new prerogative powers simply through royal declaration.

Modern judicial review continues to reflect the same underlying concern: executive authority must have a lawful basis.

5.2 Prerogative powers cannot override common law

The prerogative must also operate consistently with the common law.

The common law includes principles developed through judicial decisions, including principles concerning the limits of public authority and the protection of legal rights.

In Miller [2017] UKSC 5, the Supreme Court emphasised that prerogative powers could not be used to change domestic common law or statute law.

This principle is significant because it prevents ministers from treating historical executive authority as superior to the legal framework within which that authority exists.

The relationship between prerogative and common law is therefore one of legal recognition and limitation. The common law recognises certain executive powers, but it also determines their boundaries.

5.3 Public power and legal accountability

The rule of law requires that public authorities remain accountable for the lawful exercise of their powers.

Where a minister exercises a prerogative power, the legal consequences may affect individuals, public institutions or the constitutional system as a whole.

The courts may be asked to determine whether the claimed power exists, whether the relevant legal limits have been respected and whether the decision is capable of judicial determination.

Not every disagreement with a government decision creates a legal claim. Nor can courts necessarily determine every question involving foreign affairs or national security.

Nevertheless, the prerogative does not provide a general exemption from judicial scrutiny.

The legal question is not whether the power has historical royal origins, but whether the matter raises a legal issue that the courts can properly determine.

6. Judicial Review of the Royal Prerogative

Judicial review is a central mechanism through which the courts supervise the legality of executive action.

Its significance for the royal prerogative lies in the distinction between the existence of an executive power and the lawfulness of its exercise.

A prerogative power may exist, yet a particular decision made under that power may be unlawful. Alternatively, the Government may claim to exercise a power that does not legally exist in the form asserted.

The courts can determine these questions where they fall within their jurisdiction.

6.1 Can prerogative powers be judicially reviewed?

Yes, many exercises of prerogative power can be subject to judicial review.

The fact that a power originates in the common law rather than legislation does not automatically prevent a court from examining it.

However, judicial review does not mean that every decision made under the prerogative will be examined in the same way. The nature of the power, the subject matter and the legal question involved are relevant.

Some matters involve questions that courts can determine by applying established legal standards. Other matters may involve issues of political judgment, operational expertise or national security that are difficult or inappropriate for judicial determination in the particular form presented.

The central distinction is between the existence and legal limits of a power and the merits of a decision made within those limits.

Courts can determine whether a minister has acted beyond the legal authority available. They do not automatically acquire a general power to substitute their preferred foreign policy, defence strategy or political judgment for that of the Government.

6.2 The GCHQ case

An important development in the judicial review of prerogative powers occurred in Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374, commonly known as the GCHQ case.

The case concerned a government decision affecting trade union membership at Government Communications Headquarters.

The relevant power was exercised under the royal prerogative rather than a statutory provision. The House of Lords established that the source of a power was not, by itself, decisive in determining whether its exercise could be reviewed.

Instead, the nature and subject matter of the decision were central to the question of reviewability.

The case established an important principle: prerogative powers are not categorically immune from judicial review merely because they derive from the Crown’s historical authority.

However, the case also illustrates the limits of judicial review. The House of Lords accepted that national security considerations could justify the Government’s decision in the circumstances, notwithstanding the procedural fairness arguments advanced by the claimants.

The decision therefore demonstrates both the reach and the restraint of judicial supervision.

It recognises that legal limits apply to executive power while acknowledging that some questions involve responsibilities and judgments that the courts must approach with appropriate care.

6.3 The distinction between legality and political merits

Judicial review ordinarily examines the lawfulness of a decision rather than whether it represents the best political choice.

For example, a court may determine whether a minister has acted within the authority conferred by a statute or whether a prerogative power permits the action in question.

It does not follow that the court may replace the Government’s decision simply because the judge considers another policy more effective.

This distinction is particularly important in foreign affairs and national defence, where decisions may involve complex assessments and competing political considerations.

Nevertheless, the Government cannot make a decision immune from legal scrutiny merely by describing it as political.

If the claim raises a question about the legal existence or limits of the power, the courts may have to determine that question.

6.4 The importance of effective remedies

Where a court finds that an exercise of prerogative power is unlawful, it may grant an appropriate judicial remedy.

Depending on the circumstances and the nature of the proceedings, this may include a quashing order, a declaration or another form of relief available under the relevant legal framework.

The purpose of the remedy is to address the legal defect identified by the court.

The appropriate remedy will depend on the nature of the unlawful decision and the consequences of granting relief. The court does not necessarily determine every subsequent political or administrative step that must follow.

Judicial review therefore operates as a mechanism for enforcing legal limits rather than as a general system of judicial administration of government.

7. Landmark Case Study: Miller [2017] UKSC 5

The first Miller case is one of the most important modern authorities on the relationship between the royal prerogative, parliamentary sovereignty and domestic law.

It arose from the Government’s intention to notify the European Council under Article 50 of the Treaty on European Union, thereby initiating the formal process of the UK’s withdrawal from the EU.

The Government argued that the notification could be given under the royal prerogative associated with foreign affairs and treaty-making.

The claimants argued that the Government could not use the prerogative to initiate a process that would change domestic law and remove statutory rights created through the European Communities Act 1972.

7.1 The constitutional issue

The central question was whether ministers could exercise the royal prerogative to give Article 50 notification without prior authorisation from Parliament.

The Government’s position relied on the traditional executive role in international relations. The claimants argued that withdrawal would affect rights and legal arrangements established by domestic legislation.

The dispute therefore required the Court to examine the relationship between international executive authority and domestic parliamentary sovereignty.

7.2 The Supreme Court’s decision

The Supreme Court held, by a majority, that the Government could not give Article 50 notification using the prerogative alone.

The Court reasoned that the European Communities Act 1972 had created a statutory framework through which EU law had effect in domestic law. Withdrawal would inevitably result in changes to that framework and the removal of statutory rights.

The prerogative could not be used to bring about those changes without parliamentary authorisation.

The decision did not mean that ministers had no role in foreign affairs or that every international agreement required a separate Act of Parliament.

Rather, the Court distinguished between conducting international relations and using executive powers to change domestic law or remove statutory rights.

The constitutional principle was that changes to domestic law of this kind required lawful parliamentary authority.

7.3 Why the case matters

The judgment established an important limitation on executive power.

It confirmed that the Government cannot rely on the royal prerogative to achieve a result that the law reserves to Parliament.

This principle protects parliamentary sovereignty by ensuring that executive authority does not become a substitute for legislation when statutory rights or domestic legal arrangements would be altered.

The case also illustrates that the royal prerogative remains a relevant source of executive power, but its scope must be understood in the context of the wider legal system.

The official judgment is available at Miller [2017] UKSC 5.

Constitutional Insight

The Miller judgment demonstrates that constitutional authority is not determined solely by the identity of the institution exercising it. The decisive question is whether the proposed action falls within the legal authority available to that institution.

8. Landmark Case Study: Miller/Cherry [2019] UKSC 41

The second Miller case concerned the Government’s advice to the Queen to prorogue Parliament in 2019.

The Prime Minister advised that Parliament should be prorogued for a period that would prevent it from sitting for several weeks during a politically significant period preceding the UK’s scheduled departure from the European Union.

The Government argued that the decision concerned a prerogative power and was not a matter for judicial determination.

The claimants argued that the prorogation was unlawful because it frustrated Parliament’s ability to perform its constitutional functions.

The case raised fundamental questions about parliamentary sovereignty, ministerial accountability and the legal limits of prerogative power.

8.1 The constitutional issue

The Supreme Court considered two principal questions.

First, whether the legality of the Prime Minister’s advice to prorogue Parliament was a matter that the courts could determine.

Second, if the issue was justiciable, whether the advice was lawful.

The Court distinguished between the political decision to prorogue Parliament within lawful limits and the legal question of whether the power had been exercised beyond those limits.

The issue was not simply whether the Government had chosen an appropriate political strategy. It was whether the exercise of the prerogative had crossed a constitutional boundary established by law.

8.2 The Supreme Court’s decision

On 24 September 2019, the Supreme Court unanimously held that the advice to prorogue Parliament was unlawful.

The Court concluded that a decision to prorogue Parliament, or to advise the monarch to do so, would be unlawful if it had the effect of frustrating or preventing Parliament from carrying out its constitutional functions without reasonable justification.

The prorogation in question had that effect. It prevented Parliament from performing its legislative and scrutiny functions for a significant period, and the Government had not provided a reasonable justification for that interference.

The Court therefore concluded that the advice was unlawful and that the resulting prorogation was null and of no effect.

The decision was significant because it confirmed that the existence of a prerogative power did not prevent the courts from determining its legal limits.

The official case summary and judgment are available at Miller/Cherry [2019] UKSC 41.

8.3 Why the judgment matters

The case demonstrates the relationship between the royal prerogative and the separation of powers.

The Government possessed a role in advising the monarch on prorogation, but that role was not unlimited. The exercise of the power could not lawfully undermine Parliament’s ability to perform its constitutional functions without reasonable justification.

The judgment also clarified the distinction between legal review and political decision-making.

The Court did not claim a general authority to determine when Parliament should sit or to direct the Government’s political programme. It established a legal standard for determining whether the prerogative had been exercised within its constitutional limits.

The case therefore illustrates how judicial review can protect parliamentary sovereignty and accountability without transferring the general functions of government to the judiciary.

8.4 The constitutional significance of the case

The judgment is especially important because it demonstrates that constitutional principles can impose legal limits on prerogative powers even where no single statute comprehensively defines the power in question.

The Court relied on fundamental constitutional principles concerning parliamentary sovereignty and parliamentary accountability to determine the limits of the prorogation power.

The case also confirms that political sensitivity does not automatically make a legal question non-justiciable.

A decision may be politically controversial and still raise a legal question that courts can properly determine.

However, the judgment should not be interpreted as establishing that every exercise of the prerogative is reviewable on identical grounds. The Court addressed the particular constitutional power and the specific interference with Parliament’s functions presented by the case.

9. Which Prerogative Powers Are Subject to Judicial Review?

The judicial review of prerogative powers depends on the nature of the power and the legal issue raised.

There is no general rule that all prerogative powers are immune from review. Equally, there is no rule that every decision made under the prerogative can be examined in every respect by a court.

The distinction between legal limits and political merits remains central.

9.1 Powers involving legal boundaries

Where the existence or scope of a prerogative power is disputed, the courts may determine the relevant legal question.

For example, the courts can examine whether ministers possess the authority to take a particular action or whether a claimed power conflicts with legislation.

The Miller cases demonstrate that courts may determine the legal limits of prerogative powers even where the issues have major political consequences.

9.2 Foreign affairs and national security

Decisions concerning foreign affairs and national security may involve complex judgments and sensitive information.

The fact that a matter concerns these subjects does not automatically prevent judicial review. However, the nature of the decision may affect whether particular issues can be determined through judicial proceedings and the extent of the court’s scrutiny.

The GCHQ case illustrates this distinction. The source of the power did not automatically prevent review, but the national security considerations involved were relevant to the outcome.

9.3 The prerogative of mercy and other sensitive powers

Historically, some prerogative powers were regarded as especially unsuitable for judicial review because of their subject matter.

The law has developed beyond a simple categorical distinction between reviewable and non-reviewable powers. Courts may examine legal questions concerning prerogative decisions in circumstances where such questions can properly be determined.

However, the scope of review depends on the particular power, the applicable legal principles and the nature of the challenge.

It would therefore be inaccurate to suggest either that all exercises of the prerogative are immune from review or that all are subject to identical judicial standards.

9.4 The role of judicial restraint

Judicial restraint is an important feature of the modern constitutional system.

Courts must determine legal disputes independently, but they must also respect the constitutional responsibilities of other institutions.

A court examining the legality of an executive decision should not automatically replace a political judgment with its own preferred approach.

The proper task is to determine whether the decision falls within the lawful authority available to the executive and whether the relevant legal requirements have been satisfied.

The balance between effective judicial supervision and respect for the responsibilities of government is one of the most important questions in the law of the royal prerogative.

10. The Royal Prerogative and Constitutional Conventions

The royal prerogative cannot be understood fully without considering constitutional conventions.

Conventions are established constitutional practices that guide how public institutions exercise their powers and relate to one another. They may be politically binding even where they are not directly enforceable by courts in the same way as statutory provisions.

The modern relationship between the monarch and ministers depends heavily on conventions.

10.1 Acting on ministerial advice

The monarch generally acts on ministerial advice when exercising prerogative powers.

This convention reflects the development of parliamentary government and the principle that political responsibility should rest with ministers rather than the sovereign personally.

The formal exercise of a prerogative power may involve the Crown, but the political decision and its consequences ordinarily belong to the Government.

The convention is central to the constitutional position of the monarchy. It allows the sovereign to retain formal constitutional functions while avoiding direct involvement in ordinary political disputes.

10.2 Ministerial responsibility

Ministers are accountable to Parliament for the exercise of executive authority, including advice given to the monarch.

This accountability helps prevent the formal role of the Crown from obscuring political responsibility.

Where a minister advises the monarch to exercise a prerogative power, the relevant minister may be expected to explain the decision and defend its legality and policy justification.

The Government cannot ordinarily avoid responsibility by arguing that the formal act was performed by the monarch.

The constitutional structure therefore connects prerogative authority with ministerial responsibility.

10.3 The distinction between conventions and law

Although conventions are important, they must be distinguished from legal rules.

A constitutional convention may establish an expectation about how a power should be exercised without creating a directly enforceable legal obligation in every circumstance.

Courts may recognise the existence of a convention or consider it relevant to a constitutional dispute, but they do not automatically enforce conventions as if they were statutory provisions.

The legal question remains whether the relevant conduct breaches an enforceable legal rule or falls outside the lawful limits of a power.

The distinction is especially important in disputes concerning the monarch’s formal role. The legal authority for a prerogative power and the conventions governing its exercise may be related, but they are not identical.

Constitutional Insight

Conventions help make constitutional government workable by guiding conduct where legislation does not prescribe every detail. Their importance, however, does not eliminate the need to distinguish political obligations from enforceable legal limits.

11. The Royal Prerogative and the Separation of Powers

The royal prerogative provides a practical illustration of the separation of powers in the United Kingdom.

The executive exercises certain powers recognised by the common law, but Parliament retains the authority to legislate on the relevant subjects, and the courts may determine the legal boundaries of executive action.

This arrangement does not create a rigid separation between the branches. Instead, it establishes a system in which different institutions have distinct responsibilities and may scrutinise the exercise of public power in different ways.

11.1 The executive’s constitutional role

The Government requires authority to conduct foreign relations, manage national defence and perform other functions that cannot be reduced to the enactment of legislation alone.

The royal prerogative provides a legal basis for certain executive actions that remain recognised at common law.

However, the existence of these powers does not allow the executive to determine its own authority without legal constraint.

The Government must exercise prerogative powers within their recognised scope and consistently with applicable legislation.

11.2 Parliament’s legislative authority

Parliament may regulate the exercise of prerogative powers through legislation.

It can establish statutory procedures, restrict executive discretion or replace prerogative arrangements with a statutory scheme.

The relationship between statute and prerogative is therefore one of continuing constitutional interaction.

The executive may possess authority under the prerogative, but that authority must operate within the legal framework established by Parliament.

11.3 The judiciary’s supervisory role

The judiciary determines legal disputes concerning the existence and limits of prerogative powers.

The courts do not possess a general authority to direct government policy. Their role is to determine the lawfulness of the action challenged and grant an appropriate remedy where the legal requirements are satisfied.

The Miller cases demonstrate that judicial review can protect parliamentary sovereignty and accountability by preventing the executive from exceeding the limits of its authority.

The separation of powers is therefore maintained not by eliminating every interaction between institutions but by ensuring that each institution operates within its constitutional responsibilities.

12. The Royal Prerogative in England and Wales and the Wider United Kingdom

The royal prerogative is part of the constitutional framework of the United Kingdom, but its operation must be understood in the context of the UK’s territorial constitutional arrangements.

England and Wales share a legal jurisdiction, while Scotland and Northern Ireland have distinct legal systems. Devolution also distributes legislative and executive responsibilities among institutions operating at different levels of government.

The UK Government exercises certain prerogative powers on a UK-wide basis, while responsibility for particular matters may be affected by devolved arrangements and the relevant legal framework.

The precise position depends on the power concerned.

12.1 The legal system of England and Wales

Within England and Wales, the courts may determine disputes concerning the lawfulness of executive action, including action taken under prerogative powers.

The High Court and other courts exercise jurisdiction according to the relevant legal and procedural rules. Judicial review may be available where a claimant challenges the legality of a decision made by a public authority.

The principles governing the existence and limits of prerogative powers are part of the wider common law framework and may have significance throughout the UK.

However, the relevant legislation, institutional responsibilities and remedies must be considered in the context of the particular legal system and claim.

12.2 Devolution and prerogative powers

Devolution has introduced additional constitutional relationships involving the UK Government, the devolved administrations and the relevant legislatures.

The Scottish Parliament, Senedd and Northern Ireland Assembly exercise legislative powers within their respective statutory frameworks. Their executive institutions also have defined responsibilities.

Prerogative powers must be considered in light of these arrangements, particularly where a decision concerns a subject connected with devolved responsibilities.

The existence of a UK-wide prerogative power does not automatically answer every question about the constitutional responsibilities of devolved institutions or the legal consequences of a particular decision.

The relevant legal framework must be examined carefully.

12.3 Why the distinction matters

The royal prerogative is often discussed as if it were a single national power operating identically in every legal context.

In reality, the constitutional arrangements of the United Kingdom are more complex. The source of a power, the institution responsible for exercising it and the legal consequences of its use may depend on the particular subject and jurisdiction.

For an encyclopedia concerned with England and Wales, the central task is to explain the common law principles governing prerogative authority while identifying the wider UK constitutional arrangements where they materially affect the analysis.

13. Practical Examples of the Royal Prerogative

The doctrine becomes clearer when considered through practical examples.

Example 1: The Government seeks to alter domestic law through prerogative powers

Suppose the Government enters an international arrangement that would require the removal of statutory rights currently recognised in domestic law.

The Government cannot assume that its authority to conduct foreign affairs permits it to remove those rights without parliamentary authorisation.

The legal question is whether the proposed action would change domestic law or interfere with statutory rights in a way that requires legislation.

The Miller judgment demonstrates that the prerogative cannot be used to achieve changes that the constitution reserves to Parliament.

Example 2: A minister advises the monarch to prorogue Parliament

Suppose the Prime Minister advises the monarch to prorogue Parliament for an unusually long period during a politically sensitive period.

The fact that prorogation is a prerogative power does not automatically make the advice lawful.

A court may consider whether the decision has the effect of frustrating or preventing Parliament from carrying out its constitutional functions without reasonable justification.

The 2019 Miller/Cherry judgment establishes that such a decision may be unlawful where it crosses the constitutional limits identified by the Supreme Court.

Example 3: The Government makes a decision involving national security

Suppose the Government takes an executive decision involving national security and the decision is challenged in court.

The court must first consider whether the matter raises a legal question that can properly be determined through judicial review.

The fact that the decision involves national security does not automatically exclude review. However, the nature of the decision and the evidence may affect the scope of the court’s examination.

The GCHQ case illustrates that judicial review and appropriate judicial restraint can operate together.

Example 4: Parliament replaces a prerogative arrangement with legislation

Suppose Parliament enacts legislation regulating a matter previously governed by prerogative powers.

The Government must comply with the statutory framework. It cannot ordinarily rely on the prerogative to avoid conditions imposed by Parliament.

The precise effect depends on the wording and scope of the Act, but the general principle is that executive authority must remain consistent with the law.

Example 5: The monarch formally appoints a Prime Minister

Suppose a general election produces a result in which the ability of a particular political leader to command the confidence of the House of Commons must be established.

The monarch formally appoints the Prime Minister according to the relevant constitutional arrangements.

The appointment is not an invitation for the monarch to select a preferred political programme. Constitutional conventions require the appointment to reflect the parliamentary position and the formation of a government capable of commanding the necessary confidence.

This example illustrates the distinction between formal royal authority and political responsibility within the modern constitutional system.

14. Key Takeaways

The royal prerogative is a body of powers recognised by the common law as belonging historically to the Crown. In modern practice, many are exercised by ministers under constitutional conventions.

The prerogative is not a single unrestricted power to govern. Each prerogative power has its own scope and legal limitations.

Prerogative powers must be distinguished from statutory powers. Statutory powers derive from legislation, while prerogative powers derive from the common law.

The royal prerogative cannot ordinarily be used to change domestic statute law or common law, remove statutory rights without proper authority or circumvent an applicable statutory framework.

The monarch generally acts on ministerial advice in the exercise of prerogative powers. Ministers bear political responsibility for their decisions and may be required to account to Parliament.

Prerogative powers are not automatically immune from judicial review. Courts may determine whether a power exists, establish its legal limits and examine whether its exercise is lawful.

The GCHQ case established that the source of a power is not, by itself, decisive in determining whether judicial review is available. The nature and subject matter of the decision are also relevant.

In Miller [2017] UKSC 5, the Supreme Court held that the Government could not use the prerogative alone to give Article 50 notification because the process would inevitably affect domestic law and statutory rights.

In Miller/Cherry [2019] UKSC 41, the Supreme Court held that the advice to prorogue Parliament was unlawful because it frustrated or prevented Parliament from performing its constitutional functions without reasonable justification.

The royal prerogative operates alongside parliamentary sovereignty, the rule of law, ministerial responsibility and judicial independence.

The precise operation of prerogative powers must be considered within the wider constitutional arrangements of the United Kingdom, including the distinct legal systems and devolved institutions.

15. Frequently Asked Questions

What is the royal prerogative in UK law?

The royal prerogative is a body of powers recognised by the common law as belonging historically to the Crown. In modern practice, many of these powers are exercised by ministers on behalf of the Crown.

They include certain functions associated with foreign affairs, national defence, appointments, honours and the summoning or prorogation of Parliament. Each power has its own legal scope and limitations.

Does the monarch personally exercise the royal prerogative?

The monarch formally exercises certain prerogative powers, but the modern constitutional system generally requires the sovereign to act on ministerial advice.

Political responsibility ordinarily rests with ministers, who are accountable to Parliament for their decisions. The formal role of the Crown must therefore be distinguished from the practical exercise of executive authority.

What is the difference between royal prerogative and statutory power?

A statutory power is created or conferred by legislation. Its scope and conditions are determined by the relevant Act.

A prerogative power is recognised by the common law rather than created by a specific statutory provision.

Both types of power are subject to legal limits. The prerogative cannot ordinarily be used to override legislation or frustrate its purpose.

Can the royal prerogative override an Act of Parliament?

No. Under the orthodox constitutional principles governing the prerogative, executive powers cannot ordinarily be used to change domestic statute law or circumvent an applicable statutory framework.

Where Parliament has legislated on a matter, the Government must comply with the relevant law.

Can the royal prerogative be abolished?

Parliament can legislate to restrict, regulate or remove prerogative powers, or replace them with statutory arrangements.

The effect of legislation depends on its wording and the relevant legal principles. Not every statute affecting a subject automatically abolishes every associated prerogative power.

Can courts review the exercise of the royal prerogative?

Yes. Many exercises of prerogative power can be subject to judicial review.

Courts may determine whether a power exists, establish its legal limits and examine whether its exercise is lawful. The availability and scope of review depend on the nature of the power and the legal issues raised.

What was decided in the GCHQ case?

In Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374, the House of Lords established that the source of a power was not, by itself, decisive in determining whether it could be reviewed.

The case demonstrated that prerogative powers are not automatically immune from judicial review. It also illustrated that national security considerations may be relevant to the outcome.

What was the significance of Miller [2017] UKSC 5?

The Supreme Court held that the Government could not use the royal prerogative alone to notify the European Union under Article 50 because the process would inevitably affect domestic law and statutory rights created through legislation.

The case confirmed that the executive cannot use prerogative authority to bring about changes that require parliamentary authorisation.

What was the significance of Miller/Cherry [2019] UKSC 41?

The Supreme Court held that the advice to prorogue Parliament was unlawful because the prorogation frustrated or prevented Parliament from performing its constitutional functions without reasonable justification.

The case confirmed that the courts can determine the legal limits of the prerogative power to prorogue Parliament.

Does the royal prerogative apply to foreign affairs?

Certain aspects of foreign affairs and international relations have historically been associated with the prerogative.

However, the exercise of these powers must be considered alongside applicable legislation, constitutional conventions and the distinction between international action and domestic legal consequences.

The Government cannot assume that every international decision automatically changes domestic law.

Is the royal prerogative the same as the Crown’s ceremonial role?

No. The Crown’s ceremonial functions and the royal prerogative are related but distinct concepts.

Some prerogative powers have important legal consequences, even where their formal exercise involves established constitutional ceremonies. The legal significance of a power depends on its nature and scope, not simply on whether its exercise is ceremonial.

How does the royal prerogative relate to the separation of powers?

The royal prerogative provides a source of executive authority, but Parliament may legislate to regulate it and courts may determine its legal limits.

The doctrine therefore illustrates the interaction between executive power, parliamentary sovereignty and judicial review.

Is every exercise of the royal prerogative subject to judicial review?

No. Although prerogative powers are not categorically immune from judicial review, the availability and scope of review depend on the particular power, the nature of the decision and the legal issues involved.

Courts may determine legal boundaries while exercising appropriate restraint in matters involving political judgment, national security or other considerations relevant to the constitutional responsibilities of government.

Conclusion

The royal prerogative occupies a distinctive position within the United Kingdom’s constitutional system. It preserves certain powers historically associated with the Crown while allowing them to operate within a modern framework of parliamentary government, ministerial accountability and the rule of law.

Its continuing significance lies not in the survival of unrestricted royal authority, but in the way historical executive powers have been incorporated into a constitution that distinguishes formal authority from political responsibility.

The monarch remains the formal constitutional source of many prerogative powers, but their modern exercise generally depends on ministerial advice and established conventions. Ministers, in turn, must exercise those powers within the limits recognised by law and remain accountable for their decisions.

Parliamentary sovereignty places an essential constraint on the prerogative. The Government cannot ordinarily use historical executive authority to change domestic law, remove statutory rights or evade legislation enacted by Parliament. Where a statutory framework governs a particular subject, the executive must comply with that framework.

The courts play an equally important role in determining the legal boundaries of prerogative authority. Judicial review does not transform judges into administrators or give them a general power to replace political decisions with their own preferences. It ensures that the existence and exercise of public power remain subject to legal standards.

The judgments in Miller [2017] UKSC 5 and Miller/Cherry [2019] UKSC 41 demonstrate the importance of these principles. The first confirmed that prerogative authority could not be used to bring about changes to domestic law and statutory rights that required parliamentary authorisation. The second established that the power to prorogue Parliament was limited by constitutional principles protecting Parliament’s ability to perform its legislative and scrutiny functions.

Together, these decisions illustrate that the royal prerogative must be understood within the wider constitutional system rather than as an independent source of unlimited executive authority.

The doctrine also demonstrates the relationship between constitutional continuity and legal change. A power may originate in an earlier form of government and remain part of the modern constitution, but its exercise must be understood according to contemporary legal principles and institutional responsibilities.

Ultimately, the royal prerogative illustrates a fundamental proposition of constitutional law: historical authority may explain the origin of a power, but it does not determine the full extent of its lawful exercise. The modern constitution requires executive power to remain legally defined, politically accountable and subject to appropriate judicial scrutiny.

The royal prerogative therefore survives not as an exception to constitutional government, but as a part of the constitutional framework through which the limits of executive authority continue to be defined and enforced.