## Introduction

Error of law is a primary ground for judicial review in UK public law. It arises where a public body misinterprets a statute, applies the wrong legal test, misdirects itself about relevant and irrelevant considerations, or acts contrary to binding case law. Because the court is the final arbiter of law, such errors can render decisions unlawful and liable to be quashed.

This guide sets out what counts as an error of law, how courts analyse it, the evidence you need to prove it, and what remedies are available. We highlight the leading authorities, including Anisminic, Wednesbury, Fitzpatrick and ClientEarth, and give practical steps for bringing or defending a claim.

## What You’ll Learn

- What “error of law” means in judicial review
- The difference between jurisdictional and non-jurisdictional error after Anisminic
- Common forms of legal error, with examples
- How standards of review (e.g. Wednesbury) interact with legal errors
- How to build evidence to show a legal mistake
- The role of precedent and statutory interpretation
- Remedies when an error of law is found, and when relief may be refused

## Core Concepts

### Jurisdictional vs Non-Jurisdictional Error

- Traditional approach
  - Jurisdictional error: going beyond the legal power granted by statute (e.g. acting for an improper purpose or misunderstanding the scope of a power). Such errors made a decision void.
  - Non-jurisdictional error: a mistake within the decision-maker’s sphere of authority, potentially making the decision voidable only.

- Modern position after Anisminic Ltd v Foreign Compensation Commission [1969] 2 AC 147
  - The House of Lords treated errors of law as going to jurisdiction in substance. In practice, any material legal error can invalidate a decision.
  - Ouster clauses are read narrowly; a statutory attempt to exclude review does not usually protect decisions tainted by legal error.

- Ex p Page [1993] AC 682
  - Confirmed that all errors of law by inferior bodies are, in principle, reviewable by the High Court, with limited exceptions (e.g. certain domestic bodies interpreting their own rules).

Tip: Focus less on labels and more on whether the legal mistake affected the exercise of power. If it did, the decision is vulnerable.

### Common Forms of Error of Law

- Misinterpreting statutory language
  - Reading words too narrowly or broadly, or overlooking context and purpose.
  - Fitzpatrick v Sterling Housing Association Ltd [2001] 1 AC 27 shows how the meaning of a statutory term (“family” in the Rent Act 1977) is a legal question for the court.

- Applying the wrong legal test or threshold
  - Using an incorrect test, mis-stating the elements to be satisfied, or setting an unlawful policy threshold.

- Ignoring relevant considerations or taking irrelevant ones into account
  - Relevance is determined by law. If a decision-maker disregards mandatory factors or relies on matters the statute does not permit, that is a legal error.

- Fettering discretion or unlawful delegation
  - Treating policy as rigid rule, or delegating a power that must be exercised personally, can be a legal misdirection.

- Disregarding binding precedent
  - Failing to follow a higher court’s decision on the same point of law is an error of law.

- Misapplication of EU/retained EU law or human rights law
  - ClientEarth [2015] UKSC 28 illustrates that non-compliance with EU obligations is a legal error the court can correct with mandatory orders.

- Mistake of fact affecting the legal test
  - While an error of fact is distinct, a material mistake about an established and uncontentious fact can justify quashing if it undermines the legal analysis (see E v Secretary of State for the Home Department [2004] QB 1044).

### Standard of Review and Reasons

- Court decides questions of law
  - The interpretation of legislation and binding caselaw is for the court. On pure law, the court applies its own judgment, not a “range of reasonable views”.

- Reasonableness (Wednesbury) for evaluative judgments
  - Where the issue is a judgment or policy choice within the statutory remit, the court asks whether the decision was so irrational that no reasonable authority could have made it (Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223).
  - Reasonableness review can be applied with more or less intensity depending on context (e.g. rights, serious impacts), but it is not a merits appeal.

- Reasons and transparency
  - Some statutes require reasons; even where they do not, lack of reasons can hinder the authority’s ability to show it applied the correct legal test.
  - In judicial review, public bodies owe a duty of candour: they must assist the court with the relevant legal and factual material.

### Proving an Error of Law: What to Show

- Identify the governing legal rule
  - Point to statutory provisions, binding cases, and authoritative guidance showing the correct approach.

- Contrast with the decision-maker’s approach
  - Use the decision letter, reasons, policy documents, and the factual record to show a misinterpretation, wrong test, or reliance on impermissible factors.

- Demonstrate materiality
  - Explain how the legal error affected the outcome or fairness of the process. Relief can be refused if the error made no difference.

- Support with authority
  - Cite decisions on similar statutory terms or powers, and any higher court rulings the body should have followed.

## Key Examples or Case Studies

### Anisminic Ltd v Foreign Compensation Commission [1969] 2 AC 147

- Context: Commission misinterpreted eligibility conditions under an ouster clause.
- Takeaway: A material error of law vitiates a decision; ouster clauses do not shield unlawful decisions.
- Application: If a tribunal or authority misunderstands the scope or meaning of its power, the decision can be quashed.

### Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223

- Context: Cinema licence included a condition barring children on Sundays.
- Takeaway: Courts will not substitute their view for the decision-maker’s but will intervene if the outcome is so unreasonable that no reasonable body could reach it.
- Application: When alleging unreasonableness as part of a legal error, show a clear misdirection or a decision outside a lawful range.

### Fitzpatrick v Sterling Housing Association Ltd [2001] 1 AC 27

- Context: Whether a same-sex partner counted as “family” for Rent Act succession.
- Takeaway: The meaning of statutory terms is a question of law, read in context and purpose.
- Application: Where a public body narrows a statutory term without justification, argue misinterpretation supported by case law.

### R (ClientEarth) v Secretary of State for the Environment, Food and Rural Affairs [2015] UKSC 28

- Context: Government plans failed to meet EU air quality limits within required timelines.
- Takeaway: Non-compliance with EU law obligations is a legal error; courts can grant mandatory relief to secure compliance.
- Application: In regulatory contexts, check directly effective obligations and timelines. Failure to meet them is a strong legal ground.

## Practical Applications

- Read the statute first
  - Identify the power, purpose, mandatory factors, time limits, and any preconditions. Map the legal steps the authority had to follow.

- Frame the alleged legal error clearly
  - Was the wrong test used? Were required factors ignored? Did the body misread a key term? Keep grounds precise and linked to authority.

- Gather the record
  - Obtain the decision letter, reasons, policy documents, consultation materials, and minutes. Ask for reasons if unclear.

- Use binding authority
  - Support your reading with higher court cases. If there is a close analogue, explain why it governs the present decision.

- Address standard of review
  - Distinguish questions of law (for the court) from evaluative judgments (reviewed for reasonableness). Explain why the alleged error is legal, not merely a disagreement on merits.

- Show materiality
  - Anticipate the “no difference” point. Explain how the correct legal approach could have led to a different outcome or process.

- Be remedy-focused
  - Decide whether you seek a quashing order, declaration, prohibiting or mandatory order. Consider urgency and interim relief where ongoing harm exists.

- Mind procedure and timing
  - Issue proceedings promptly and within the three-month time limit. Comply with the Pre-Action Protocol and court directions.

- For public bodies: reduce risk
  - Record reasons against statutory criteria, ensure staff use the correct test, review policies for fettering, and seek legal input on difficult statutory terms.

## Summary Checklist

- Define the correct legal rule from statute and binding cases
- Identify exactly how the decision-maker misstated or misapplied the law
- Link the error to outcome or process; show why it mattered
- Distinguish law questions from merits and set out the proper standard of review
- Assemble the record: reasons, policies, minutes, relevant evidence
- Cite key authorities: Anisminic, Wednesbury, Fitzpatrick, ClientEarth
- Choose appropriate remedies and address any “no difference” argument
- File promptly and follow the procedural rules

## Quick Reference

| Concept                      | Authority                                   | Key Takeaway                                                             |
| ---------------------------- | ------------------------------------------- | ------------------------------------------------------------------------ |
| Jurisdiction after Anisminic | Anisminic [1969] 2 AC 147                   | Material legal errors invalidate decisions; ouster clauses read narrowly |
| Reviewability of legal error | R v Lord President, ex p Page [1993] AC 682 | In principle, all errors of law are reviewable, with limited exceptions  |
| Reasonableness standard      | Wednesbury [1948] 1 KB 223                  | Irrational outcomes can be set aside; not a merits appeal                |
| Meaning of statutory terms   | Fitzpatrick [2001] 1 AC 27                  | Interpretation of statutory language is for the court                    |
| EU/retained EU compliance    | ClientEarth [2015] UKSC 28                  | Failure to meet EU legal duties is an error of law                       |
| Remedies in JR               | Senior Courts Act 1981, s.31                | Quashing, prohibiting, mandatory orders; relief is discretionary         |

Error of Law in Judicial Review: Principles, Tests and Key Cases