Judicial review does not question whether a decision was good or bad policy. Instead, it asks whether the decision-maker:

• Acted within their legal powers (lawfulness).

• Followed fair procedures (fairness).

• Reached a reasonable decision (rationality).

It ensures that public authorities act within the law and respect individual rights. Judicial review applies to government departments, local authorities, the police, tribunals, and other public bodies exercising statutory powers.

Judicial review arises from the common law, not from statute, though the Senior Courts Act 1981 (s.31) sets out the modern procedure.
It embodies the rule of law, the idea that government must act according to legal authority, and supports the separation of powers by allowing the judiciary to supervise the executive.

The leading case establishing judicial review as a constitutional principle is the GCHQ case (Council of Civil Service Unions v Minister for the Civil Service [1985]), where the House of Lords confirmed that government decisions can be reviewed on legal grounds, even where they involve prerogative powers.

The modern framework for judicial review comes from Lord Diplock’s classification in the GCHQ case. There are three main grounds:

(a) Illegality

A decision is unlawful if the public body:

• Exceeds the powers granted by Parliament (acting ultra vires).

• Fails to use its powers for the proper purpose.

• Takes into account irrelevant considerations or ignores relevant ones.

Case example: Anisminic Ltd v Foreign Compensation Commission [1969], a decision made under a misinterpretation of the law was held to be void.

(b) Irrationality

A decision may be quashed if it is so unreasonable that no reasonable authority could ever have made it, known as Wednesbury unreasonableness.
Case example: Associated Provincial Picture Houses v Wednesbury Corporation [1948], a cinema licence condition was upheld, but the case established the principle of irrationality.

(c) Procedural Impropriety

A decision may be invalid if proper procedures were not followed, including breaches of natural justice (fair hearing, absence of bias) or failure to follow statutory procedural rules.
Case examples:

• Ridge v Baldwin [1964], dismissal without a hearing was unlawful.

• Pinochet (No. 2) [1999], judge’s undisclosed connection created apparent bias.

Modern developments have expanded review to include:

• Legitimate Expectation: where a public body has promised to act in a certain way and the claimant relied on that promise (R v North and East Devon Health Authority, ex parte Coughlan [2001]).

• Proportionality: especially in cases involving human rights or EU law — the court assesses whether the action taken was necessary and proportionate to the objective (R (Daly) v Secretary of State for the Home Department [2001]).

Applications for judicial review must:

• Be made promptly, within three months of the decision.

• Obtain the court’s permission (leave) to proceed, to filter out weak claims.

• Be made by someone with sufficient interest (locus standi), meaning a direct stake in the matter (R v Inland Revenue Commissioners, ex parte National Federation of Self-Employed [1982]).

If successful, the court may issue one or more remedies.

The court can issue several remedies, including:

• Quashing Order – overturns an unlawful decision.

• Prohibiting Order – prevents a public body from acting unlawfully in the future.

• Mandatory Order – compels a body to perform a public duty.

• Declaration – clarifies the legal position of the parties.

• Injunction – restrains unlawful action.

• Damages – available only where a separate legal right exists.

Remedies are discretionary; even if the claimant succeeds, the court may withhold a remedy if it would cause disproportionate harm or serve no practical purpose.