## **Learning Outcomes**

This article examines judicial control over prerogative powers in the UK constitution, including:

- The legal nature, sources, and constitutional status of prerogative powers and their relationship with statute
- The principles governing when prerogative powers are justiciable, with emphasis on GCHQ, Miller (2017), and Miller (No 2)
- The application of core judicial review grounds—illegality, irrationality, procedural impropriety, legitimate expectation, and proportionality—to prerogative decisions
- The distinction between reviewable administrative prerogatives (such as passports and the prerogative of mercy) and non-justiciable high policy areas (such as defence, foreign affairs, and honours)
- The effect of statutory displacement, abeyance, and possible revival of prerogative powers, illustrated by De Keyser, Fire Brigades Union, and the Dissolution and Calling of Parliament Act 2022
- The interaction between prerogative powers and key constitutional principles, particularly the rule of law, parliamentary sovereignty, and parliamentary accountability
- The mechanisms of parliamentary scrutiny over prerogative use, including CRaG treaty ratification procedures and conventions on war powers
- The range, limits, and practical operation of judicial review remedies in prerogative cases, including declarations, injunctions, and modern quashing orders under the Judicial Review and Courts Act 2022

## **SQE1 Syllabus**

For SQE1, you are required to understand the legal status of prerogative powers and the extent to which the courts can review their exercise, with a focus on the following syllabus points:

- The definition and scope of prerogative powers in the UK constitution
- The grounds and limits of judicial review over prerogative powers
- The distinction between reviewable and non-justiciable prerogative powers
- The relationship between prerogative powers, statute, and constitutional principles such as the rule of law and parliamentary sovereignty
- How statute can displace prerogative (e.g. Attorney General v De Keyser’s Royal Hotel) and what happens on repeal (revival of prerogative)
- The impact of R v Secretary of State for the Home Department, ex p Fire Brigades Union on using prerogative where a statutory scheme exists but is not yet commenced
- Prerogative treaty-making and the Constitutional Reform and Governance Act 2010 (CRaG) treaty ratification procedures
- The Dissolution and Calling of Parliament Act 2022 and the revival of the prerogative to dissolve Parliament
- Remedies available on judicial review, including suspended and prospective-only quashing orders under the Judicial Review and Courts Act 2022
- Accountability to Parliament for prerogative actions (e.g. war powers convention, select committees)

## **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 primary legal mechanism by which courts control the exercise of prerogative powers?
2. Which areas of prerogative power are generally considered non-justiciable by the courts?
3. Can the government use prerogative powers to override or frustrate an Act of Parliament?
4. What is the significance of the GCHQ case for judicial review of prerogative powers?
5. How do the rule of law and parliamentary sovereignty limit the exercise of prerogative powers?

## **Introduction**

Prerogative powers are historic executive powers exercised by government ministers on behalf of the Crown, existing alongside statutory powers. Judicial control over prerogative powers is essential to ensure that the executive acts within legal limits and respects constitutional principles. Courts use judicial review to scrutinise the lawfulness of prerogative actions, but there are important boundaries to this oversight. Parliamentary mechanisms also operate to scrutinise prerogative use—most notably the treaty ratification procedures under the Constitutional Reform and Governance Act 2010 (CRaG) and the convention that the House of Commons is consulted before deployment of the armed forces in most circumstances.

## The Nature and Scope of Prerogative Powers

Prerogative powers are common law powers that pre-date modern statutes. They enable the executive to act without direct parliamentary authority in certain areas, such as foreign affairs, defence, and the issuing of passports.

> **Key Term: prerogative powers**
> Prerogative powers are non-statutory executive powers historically vested in the Crown and now exercised by government ministers, covering areas not regulated by statute.

Prerogative powers cannot be expanded or created anew by the government; their scope is fixed by law. The courts decide whether a prerogative exists and define its extent. In BBC v Johns, the Court of Appeal confirmed that new prerogatives cannot be recognised in modern times. Sometimes the existence or ambit of a prerogative is clarified through litigation (for example, the recognition of a residual prerogative to maintain the peace of the realm in Northumbria Police).

Statute can abolish, limit, or replace prerogative powers. Where statute and prerogative overlap, statute prevails. Attorney General v De Keyser’s Royal Hotel established that if Parliament has provided a statutory scheme covering the same ground, the executive must use the statutory power and comply with its safeguards rather than rely on the prerogative. Conversely, if the statute is repealed, the prerogative may revive depending on the statutory framework and the intention of Parliament.

Parliament has also chosen to regulate, rather than abolish, particular prerogatives. Treaty-making remains a prerogative power, but the CRaG 2010 requires treaties to be laid before Parliament for 21 sitting days before ratification, and the House of Commons can block ratification. Dissolution of Parliament is a prerogative power that was put on a statutory basis by the Fixed-term Parliaments Act 2011, then restored as a prerogative by the Dissolution and Calling of Parliament Act 2022.

> **Key Term: non-justiciable**
> A non-justiciable matter is one the courts consider inappropriate for judicial review, often because it involves high policy or political judgment.

## Judicial Review of Prerogative Powers

The courts have developed the principle that prerogative powers are subject to judicial review, except where the subject matter is non-justiciable. The leading authority is the GCHQ case.

> **Key Term: judicial review**
> Judicial review is the process by which courts assess the lawfulness of actions or decisions by public bodies, including the exercise of prerogative powers.

In Council of Civil Service Unions v Minister for the Civil Service (the GCHQ case), the House of Lords confirmed that prerogative powers are in principle reviewable: the justiciability of a challenge depends on the subject matter rather than the source of the power. Lord Roskill suggested a list of prerogatives typically unsuitable for review (treaties, defence, mercy, honours, dissolution, appointment of ministers), but later cases have refined that approach. The courts will not examine the merits of high policy decisions but will enforce legal limits and constitutional fundamentals.

That refinement is illustrated by R (Miller) v The Prime Minister and Cherry v Advocate General for Scotland (Miller (No 2)), where the Supreme Court declared unlawful the advice to prorogue Parliament for an exceptional five-week period at a critical constitutional moment. Although prorogation is a prerogative power, the Court held that the limits of the power are constrained by constitutional principles—parliamentary sovereignty and accountability—and reviewed whether those limits had been transgressed.

### Reviewable and Non-Reviewable Prerogative Powers

The courts will review prerogative powers where the subject matter is suitable for legal determination. Examples of reviewable prerogative powers include the refusal or withdrawal of a passport, or the exercise of the prerogative of mercy. However, certain areas remain non-justiciable, such as:

- Making international treaties
- Defence of the realm and deployment of armed forces
- Dissolution of Parliament (now revived as a prerogative power)
- Granting honours

These are considered matters of "high policy" or political judgment, and the courts defer to the executive. Even in non-justiciable areas, the courts will ensure that prerogative actions do not change domestic law without statutory authority, and they may review the legal limits of the power (as in Miller (No 2)).

Passports are a classic example of reviewable exercise: in R v Secretary of State for Foreign and Commonwealth Affairs, ex p Everett, the Court of Appeal accepted review of a refusal to issue a passport because the decision involves individual rights and is of an administrative nature. The prerogative of mercy is subject to review in certain respects; the court in ex p Bentley emphasised that the power is broad but must be exercised on a correct legal understanding, and a refusal to consider relevant forms of mercy is reviewable.

Assistance to nationals abroad is largely a matter for diplomatic discretion. Courts have accepted that a blanket refusal to even consider representations may be irrational in rare cases, but they will not prescribe the content of foreign policy.

### **Worked Example 1.1**

A British citizen is refused a passport by the Home Office, with no reasons given. The individual seeks to challenge the decision.

> **Answer:** The refusal of a passport is the exercise of a prerogative power. The courts will review such a decision to ensure it is lawful, rational, and procedurally fair. The Home Office must provide a lawful reason for refusal and follow fair procedures.

## Grounds for Judicial Review of Prerogative Powers

The same grounds apply to prerogative powers as to statutory powers:

- **Illegality:** Acting beyond the scope of the prerogative or contrary to law.
- **Irrationality:** Making a decision so unreasonable that no reasonable authority would make it.
- **Procedural Impropriety:** Failing to follow fair procedures.

> **Key Term: illegality**
> Illegality means acting outside the legal limits of a power, including the prerogative.
>
> **Key Term: irrationality**
> Irrationality refers to a decision so unreasonable that no reasonable authority could have made it.
>
> **Key Term: procedural impropriety**
> Procedural impropriety is a failure to follow fair procedures or natural justice in decision-making.

In addition, legitimate expectation may arise (for example, a settled practice of consultation). In GCHQ, consultation was found to be expected but outweighed by national security concerns. Where human rights are engaged, proportionality may be relevant through the Human Rights Act 1998, and Orders in Council made under the prerogative are treated as primary legislation for HRA purposes (the appropriate remedy is a declaration of incompatibility, not striking down).

### **Worked Example 1.2**

The government signs an international treaty under prerogative powers that would require changes to domestic law. Can the treaty alter UK law without Parliament?

> **Answer:** No. While the government can enter treaties under prerogative powers, treaties cannot change domestic law without an Act of Parliament. This principle was confirmed in the Miller case.

## Limits on the Exercise of Prerogative Powers

### Statute Overrides Prerogative

Where Parliament has legislated in an area, the prerogative is displaced or put "in abeyance." The executive cannot use prerogative powers to override or frustrate an Act of Parliament.

Attorney General v De Keyser’s Royal Hotel confirmed that the executive must use statutory powers (and comply with statutory safeguards, such as compensation, where Parliament has provided a scheme) rather than the prerogative where the subject matter overlaps. R v Secretary of State for the Home Department, ex p Fire Brigades Union is equally important: the executive may not use prerogative powers to create or modify schemes in a way that undermines or frustrates the will of Parliament embodied in an uncommenced statute. The proper route is for ministers to seek repeal or amendment.

### **Worked Example 1.3**

Ministers attempt to use prerogative powers to introduce a compensation scheme that is less generous than one provided by statute.

> **Answer:** The government cannot use prerogative powers to undermine or frustrate the will of Parliament as expressed in statute. Statute prevails.

### The Rule of Law and Separation of Powers

The rule of law requires that all government action, including the exercise of prerogative powers, is subject to legal limits and review. The separation of powers ensures that the judiciary can check the executive's use of prerogative powers, while respecting the boundaries of non-justiciable matters.

The courts enforce fundamental constitutional boundaries: prerogative powers cannot be used to change domestic law (Miller (2017) on Article 50), or to frustrate the ability of Parliament to legislate and hold government to account (Miller (No 2) on prorogation). They also ensure compliance with legal rights and procedural duties: for example, access to the courts and effective remedies, and, in appropriate cases, fair consultation.

### **Worked Example 1.4**

The Prime Minister advises the monarch to prorogue Parliament for five weeks during an intense period of legislative scrutiny on a major constitutional issue. A judicial review claim argues that the prorogation frustrates parliamentary sovereignty.

> **Answer:** Although prorogation is a prerogative power, the courts may review its legal limits where constitutional fundamentals are at stake. In Miller (No 2), the Supreme Court held that an exceptional prorogation that, without reasonable justification, prevents Parliament from carrying out its constitutional functions is unlawful and of no effect.

## Key Cases and Principles

- **GCHQ case (Council of Civil Service Unions v Minister for the Civil Service):** Established that prerogative powers are generally subject to judicial review, except in areas of high policy.
- **Attorney General v De Keyser’s Royal Hotel:** Held that statutory powers displace the prerogative where the two overlap.
- **R v Secretary of State for the Home Department, ex parte Fire Brigades Union:** Confirmed that prerogative powers cannot be used to frustrate the will of Parliament.
- **R (Miller) v Secretary of State for Exiting the European Union (2017):** Held that prerogative powers could not be used to trigger Article 50 because this would change domestic law; Parliament’s authority was required.
- **R (Miller) v The Prime Minister; Cherry v Advocate General for Scotland (2019):** Held that advice to prorogue Parliament was unlawful where it frustrated Parliament without reasonable justification.
- **R v Secretary of State for Foreign and Commonwealth Affairs, ex p Everett:** Accepted review of passport decisions as administrative exercises of the prerogative.
- **R v Secretary of State for the Home Department, ex p Bentley:** Recognised review of aspects of the prerogative of mercy.
- **BBC v Johns:** Confirmed that no new prerogative powers can be created.
- **R v Secretary of State for the Home Department, ex p Northumbria Police Authority:** Discussed the existence and scope of a prerogative to maintain the peace of the realm.
- **M v Home Office; Factortame (No 2):** The courts can grant injunctions against ministers and enforce their orders, underscoring the rule of law.
- **Constitutional Reform and Governance Act 2010:** Subjects ratification of treaties to Parliamentary scrutiny without altering the prerogative power to make treaties.

### **Exam Warning**

> The courts will not review the merits of decisions involving high policy, such as going to war or conducting foreign relations. Judicial review is limited to questions of lawfulness, not political wisdom.

## Remedies and Practical Consequences

If a prerogative power is exercised unlawfully, the courts may grant remedies such as quashing the decision, ordering the executive to act lawfully, or requiring fair procedures. Declaratory relief is common, and injunctions can be issued against ministers. The courts will not substitute their own decision for that of the executive in matters of high policy, but they will enforce legal boundaries and require compliance with statutory frameworks.

In appropriate cases, the court may use remedial flexibility. Under the Judicial Review and Courts Act 2022, quashing orders may be suspended (to allow orderly correction) or be made prospective-only (to protect reliance interests). These tools may be applied where they are compatible with the nature of the illegality and the public interest.

### **Worked Example 1.5**

A minister refuses to issue a passport based on a rigid unpublished policy that excludes any consideration of exceptional circumstances. The individual seeks a quashing order and disclosure of the policy.

> **Answer:** The court can review the refusal on grounds of illegality (fettering discretion), irrationality and procedural fairness. It may quash the decision, require the minister to consider the application lawfully, and order disclosure of relevant policy criteria. Depending on context, a suspended quashing order may be considered to allow administrative correction without causing unfair disruption.

## **Key Point Checklist**

_This article has covered the following key knowledge points:_

- Prerogative powers are historic executive powers exercised by ministers on behalf of the Crown.
- Statute can abolish, limit, or override prerogative powers; statute prevails in case of conflict (De Keyser). On repeal, prerogatives may revive.
- Judicial review is available to challenge the lawfulness of prerogative powers, except in non-justiciable areas.
- The courts apply the same grounds of review—illegality, irrationality, and procedural impropriety—to prerogative powers as to statutory powers, alongside legitimate expectation and proportionality where applicable.
- High policy areas such as national security, defence, and treaty-making are generally non-justiciable; merits are not reviewed.
- The rule of law and parliamentary sovereignty limit the exercise of prerogative powers and underpin judicial oversight.
- The executive cannot use prerogative powers to change domestic law or to frustrate the will of Parliament (Miller 2017; Fire Brigades Union).
- Prorogation and dissolution are prerogative powers, but prorogation is reviewable in exceptional circumstances where constitutional fundamentals are at risk (Miller (No 2)); dissolution has been revived by the Dissolution and Calling of Parliament Act 2022.
- Treaty-making remains prerogative, but CRaG 2010 provides parliamentary scrutiny of ratification; treaties do not alter domestic law without legislation.
- Courts can grant effective remedies against ministers and have additional flexibility through suspended and prospective-only quashing orders (Judicial Review and Courts Act 2022).

## **Key Terms and Concepts**

- prerogative powers
- non-justiciable
- judicial review
- illegality
- irrationality
- procedural impropriety


Prerogative powers - Judicial control over prerogative powers