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This lesson examines judicial review — the single most important mechanism by which the judiciary holds the executive to account between elections. Judicial review allows the courts to assess whether the decisions, actions, and omissions of public bodies are lawful, ensuring that the government, its ministers, and public agencies act within the boundaries the law sets for them. For Edexcel A-Level Politics, Component 2 (UK Government, Section A), judicial review is central to understanding the relationship between the judiciary and the other branches of government, and to evaluating whether the courts have become too powerful. The defining feature to grasp from the outset is that judicial review polices legality, not policy: judges ask whether a decision-maker stayed within their powers and acted fairly, not whether the decision was wise or popular. Keeping that distinction sharp is the key to a strong answer on this topic.
Judicial review is the process by which courts examine the decisions, actions, or omissions of public bodies — government ministers, departments, local authorities, regulators, and other public agencies — to determine whether they are lawful. It is a supervisory jurisdiction: the court supervises how public power has been exercised, rather than acting as a court of appeal on the merits of the decision.
This distinction is fundamental and worth stating precisely. Judicial review does not assess whether a decision was wise, fair-minded, or good policy. It assesses only whether the decision-maker:
Key Term: Judicial review is the process by which courts determine whether a public body has acted within its legal powers, rationally, and in accordance with a fair procedure — it tests legality, not the merits of policy.
If a court finds that a public body acted unlawfully, it can grant a range of remedies — quashing the decision, requiring the body to act, or prohibiting unlawful future action — which are examined later in this lesson. A vital point for evaluation is that, even at its most assertive, judicial review reaches only the executive and other public bodies; it cannot be used to strike down an Act of Parliament, because parliamentary sovereignty places primary legislation beyond the reach of the courts.
It is helpful to distinguish judicial review from an ordinary appeal, because candidates often confuse the two. In an appeal, a higher court can substitute its own decision for that of the body below — it can decide that the original answer was simply wrong and replace it. In judicial review, by contrast, the court does not ask whether the decision was right; it asks whether it was lawfully made. If the decision was unlawful, the court typically quashes it and sends it back to be retaken properly by the original decision-maker, rather than imposing its own preferred outcome. This is why judicial review respects the proper role of elected ministers and expert bodies: the court polices the legal boundaries of the decision but leaves the decision itself, within those boundaries, to the body Parliament entrusted with it.
The conceptual foundation of judicial review is the doctrine of ultra vires, Latin for "beyond the powers". A public body acts ultra vires when it does something the law does not authorise it to do. The underlying constitutional idea is that public bodies, unlike private individuals, possess only the powers the law grants them: a private person may do anything not forbidden, but a minister or council may do only what the law positively permits.
A body may act ultra vires in several ways:
The ultra vires principle is what makes judicial review compatible with parliamentary sovereignty rather than a threat to it. On the orthodox view, when the courts strike down executive action they are not defying Parliament but enforcing it: they are ensuring that ministers stay within the limits Parliament laid down when it granted them their powers. Judicial review, on this analysis, gives effect to Parliament's will rather than overriding it — a point that is useful in rebutting the claim that judicial review is undemocratic.
A point that examiners value is that judicial review is not a fixed feature of the constitution but one that has grown dramatically since the 1960s. For much of the twentieth century the courts were highly deferential to the executive, reluctant to second-guess ministers and especially unwilling to review powers derived from the royal prerogative (the residual powers of the Crown, exercised in practice by ministers). The number of judicial review cases was small, and large areas of government action were treated as effectively immune from challenge.
From the 1960s onwards, a series of decisions signalled a more assertive judicial approach. Ridge v Baldwin (1964) revived the requirement of procedural fairness; later cases steadily widened the grounds and the range of bodies subject to review. The decisive moment came with the GCHQ case (1985), which established that even prerogative powers are, in principle, reviewable by the courts. Since then the volume of judicial review claims has risen substantially, and the courts have been willing to scrutinise government action across immigration, prisons, welfare, the environment, and — most strikingly — core constitutional questions. The expansion accelerated after the Human Rights Act 1998 gave claimants a new, rights-based avenue of challenge.
This growth is central to the debate about whether the judiciary has become too powerful. Supporters argue that more active judicial review is a welcome strengthening of accountability, filling gaps left by weak parliamentary scrutiny of the executive. Critics, including some senior judges, warn that the courts have drifted from policing legality towards reviewing the substance of political decisions. Either way, the trajectory is clear: judicial review is far more significant today than it was two generations ago, and this trend is itself a key piece of evaluative evidence.
The classic grounds for judicial review were set out by Lord Diplock in the landmark case Council of Civil Service Unions v Minister for the Civil Service (1985) — the GCHQ case. He identified three heads: illegality, irrationality, and procedural impropriety, and anticipated that proportionality might develop as a fourth. These categories remain the framework used today.
The decision-maker must correctly understand and give effect to the law that governs their power. A decision is illegal if the decision-maker:
Example: In R (Miller) v Secretary of State for Exiting the EU (2017), the Supreme Court held that ministers could not use the royal prerogative to trigger Article 50, because doing so would remove rights that Parliament had created by statute, and only Parliament could authorise that. The government had acted unlawfully — a clear instance of the illegality ground.
A decision is irrational if it is so unreasonable that no reasonable decision-maker could ever have arrived at it. This demanding test takes its name from Associated Provincial Picture Houses v Wednesbury Corporation (1948) and is known as Wednesbury unreasonableness.
The threshold is set deliberately high. The courts recognise that there is usually a range of decisions a public body could reasonably reach, and that it is not the judges' role to substitute their own preference for that of the elected or expert decision-maker. Only a decision that is genuinely outrageous in its defiance of logic will be quashed on this ground. Example: In Wednesbury itself, a local authority licensed a cinema on condition that no children under fifteen be admitted on Sundays. The cinema argued the condition was unreasonable, but the court held it was not so unreasonable that no reasonable authority could have imposed it — and so it stood. The case is therefore better known for defining the high bar than for crossing it.
A decision is procedurally improper where the decision-maker failed to follow a fair procedure. This ground protects the principles of natural justice and includes:
Example: In Ridge v Baldwin (1964), the House of Lords held that a Chief Constable who had been dismissed without being given a hearing had been denied natural justice; he was entitled to know the case against him and to respond. The case revitalised the requirement of procedural fairness in administrative decision-making.
Although Lord Diplock listed only three grounds, proportionality has since developed into a distinct and increasingly important basis of review, especially in cases engaging rights under the Human Rights Act 1998. Proportionality asks whether the means used to achieve a legitimate aim were no more intrusive than necessary. A structured four-stage test was set out in Bank Mellat v HM Treasury (No. 2) (2013):
Proportionality is a more intensive standard than Wednesbury unreasonableness. Under Wednesbury, the court asks only whether the decision fell within the range of reasonable outcomes; under proportionality, it scrutinises the decision-maker's reasoning much more closely, weighing the justification for interfering with a right. This is why proportionality is sometimes seen as bringing the courts closer to reviewing the substance of a decision, and why its growth is part of the debate about expanding judicial power.
The Human Rights Act 1998 (HRA) significantly enlarged the scope of judicial review by giving claimants new grounds based on Convention rights.
Section 6 makes it unlawful for any public authority to act incompatibly with the rights in the European Convention on Human Rights (ECHR). This means that a decision of a public body that violates a Convention right — for example, by interfering disproportionately with privacy or freedom of expression — can be challenged directly through judicial review, with proportionality as the operative test.
Section 3 requires courts to read and give effect to legislation, "so far as it is possible to do so", in a way compatible with Convention rights. This is a powerful interpretive tool: judges may "read down" or read words into a statute to render it compatible. Example: In Ghaidan v Godin-Mendoza (2004), the House of Lords used section 3 to interpret the Rent Act 1977 so that the survivor of a same-sex relationship enjoyed the same tenancy-succession rights as a surviving spouse, even though the Act referred to a person living with the tenant "as his or her wife or husband".
Where a statute simply cannot be read compatibly with Convention rights, the higher courts may issue a declaration of incompatibility under section 4. Crucially, this does not strike down or invalidate the law — the statute remains fully in force — but it signals to Parliament that the law breaches Convention rights and invites it to amend the law. Example: In the Belmarsh case (A v Secretary of State for the Home Department, 2004), the House of Lords declared the indefinite-detention provisions of the Anti-terrorism, Crime and Security Act 2001 incompatible with Articles 5 and 14 of the ECHR. The court could not abolish the scheme, but Parliament responded by replacing it with control orders under the Prevention of Terrorism Act 2005 — a textbook illustration of the limits of judicial power and of the "constitutional dialogue" between courts and Parliament.
When a court finds that a public body has acted unlawfully, several remedies may be granted. They are discretionary: even where a claimant succeeds, the court decides what remedy, if any, is appropriate.
| Remedy | Effect |
|---|---|
| Quashing order (formerly certiorari) | Declares the unlawful decision void and sets it aside |
| Mandatory order (formerly mandamus) | Requires the public body to perform a legal duty |
| Prohibiting order (formerly prohibition) | Prevents the public body from acting unlawfully in the future |
| Declaration | An authoritative statement of the legal position, without necessarily overturning the decision |
| Injunction | An order requiring a party to do, or refrain from doing, something |
| Damages | Monetary compensation, available in limited circumstances (notably some HRA claims) |
The GCHQ case repays close study because it is both the source of the modern grounds of review and a landmark on the reviewability of prerogative power. The dispute arose when the government, exercising prerogative powers, banned employees at Government Communications Headquarters (GCHQ) from belonging to trade unions, without the consultation that had previously been the practice. The Council of Civil Service Unions challenged the decision.
The outcome was, on its face, a defeat for the unions: the House of Lords held that the government was entitled to act as it did on grounds of national security, an area where the courts traditionally defer to the executive. Yet the case is celebrated for two principles of lasting importance. First, Lord Diplock set out the now-classic threefold classification of the grounds of review — illegality, irrationality, and procedural impropriety — and foresaw proportionality as a possible fourth. Second, and more profoundly, the Lords held that the exercise of prerogative power is not automatically immune from judicial review simply because it derives from the Crown; what matters is the subject matter of the power, not its historical source. This brought a vast swathe of executive action potentially within the supervisory jurisdiction of the courts. The case thus illustrates a recurring feature of judicial review: a court may defer on the particular facts while laying down principles that significantly expand its reach in future.
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