Irrationality and proportionality

Irrationality and proportionality constitute the core substantive grounds of judicial review concerned with the quality of administrative decision-making. While illegality (Week 2) asks whether a decision-maker has acted within their legal powers, irrationality and proportionality scrutinise whether the decision itself is defensible in law.

The doctrinal journey from Wednesbury unreasonableness to structured proportionality represents one of the most dynamic and contested areas of contemporary administrative law. The traditional domestic test—articulated by Lord Greene MR in Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223—sets a high threshold: a decision is irrational if it is so unreasonable that no reasonable authority could have reached it. This affords public bodies considerable latitude, reflecting a deferential judicial posture rooted in the separation of powers.

Proportionality, by contrast, emerged from European Union law and the European Convention on Human Rights. It requires structured, step-wise analysis: is the measure suitable to achieve a legitimate aim? Is it necessary, or could a less intrusive means suffice? Is the burden imposed proportionate to the benefit secured? This more rigorous standard has gained increasing traction in domestic law, especially in human rights contexts under the Human Rights Act 1998.

Key tensions animate this area. To what extent should courts second-guess executive and administrative judgments on matters of policy, expertise, or resource allocation? Does proportionality blur the line between appeal and review? How should the intensity of review vary according to subject-matter—comparing, say, national security decisions with decisions affecting personal liberty? The Supreme Court's recent decisions in Pham [2015] UKSC 19 and Keyu [2015] UKSC 69 signal incremental movement toward a general domestic proportionality standard, yet the debate remains open and academically live.

This note traces the historical emergence of irrationality, examines the principles animating both tests, considers the Human Rights Act's catalytic role, and evaluates whether English law is converging on a unified standard of substantive review.

Judicial control of administrative unreasonableness predates Wednesbury by centuries. The Court of King's Bench possessed an inherent supervisory jurisdiction over inferior tribunals and public bodies, ensuring they acted within the bounds of reason and law. Early cases treated 'unreasonableness' loosely, sometimes conflating it with illegality or procedural defect.

By the late 19th century, courts began to articulate a distinct substantive constraint. In Kruse v Johnson [1898] 2 QB 91, Lord Russell CJ held that local authority by-laws could be struck down if 'partial and unequal in their operation as between different classes' or 'manifestly unjust' or 'disclosed bad faith.' Yet the court emphasised restraint: 'the Court should be slow to condemn as invalid any by-law … on the ground of supposed unreasonableness.'

The modern formulation crystallised in Wednesbury itself. Wednesbury Corporation, exercising statutory powers to license cinemas, imposed a condition prohibiting children under 15 from Sunday performances. The claimant cinema challenged this as ultra vires. Lord Greene MR's judgment set out a tripartite structure: a decision-maker must (i) understand and give effect to the relevant statute; (ii) take into account matters they ought to, and disregard irrelevant considerations; (iii) reach a decision that is not 'so unreasonable that no reasonable authority could ever have come to it.' The third limb became known as Wednesbury unreasonableness or irrationality.

Lord Greene acknowledged this standard is demanding: 'It is true the decision must be so absurd that no sensible person could ever dream that it lay within the powers of the authority.' The rationale lay in constitutional principle: elected or accountable bodies enjoy a margin of discretion; courts must not substitute their own policy preferences. Wednesbury thus encoded judicial deference into the very definition of reviewable unreasonableness.

Over subsequent decades, Wednesbury became the dominant substantive ground. It provided a safety-net, catching decisions tainted by manifest absurdity, bad faith, or gross disproportionality, yet preserving administrative autonomy. By the 1980s, however, critiques emerged: the test was too lax, affording insufficient protection to individuals; its high threshold risked rubber-stamping executive excess. The stage was set for a more exacting standard.

Irrationality (Wednesbury unreasonableness) entails a unitary, holistic assessment: could any reasonable decision-maker have reached this decision? The focus is on outcome rather than process. A decision is irrational if:

• It is logically flawed or internally contradictory;
• It defies common sense or accepted moral standards to an extreme degree;
• It reflects bad faith, improper motive, or corruption;
• It exhibits gross disproportionality—the disadvantage inflicted vastly outweighs any benefit.

Lord Diplock in Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374 (the GCHQ case) formalised irrationality as one of three grounds of review (alongside illegality and procedural impropriety). He described it as applying 'to a decision which is so outrageous in its defiance of logic or of accepted moral standards that no sensible person who had applied his mind to the question to be decided could have arrived at it' [at 410]. This language—'outrageous,' 'defiance of logic'—underscores the high threshold.

Foundation

1. 'The Wednesbury test of unreasonableness sets too high a threshold for judicial intervention.' Discuss.

1. Explain the four-stage proportionality test and illustrate its application with reference to one decided case.

Standard

1. To what extent has the Human Rights Act 1998 undermined the continued utility of Wednesbury unreasonableness in English administrative law?

1. 'Proportionality review transforms judicial review into an appeal on the merits, thereby violating the constitutional separation of powers.' Critically assess this claim.

Challenge

1. In light of recent Supreme Court case law, evaluate whether English law should adopt proportionality as a general common law ground of judicial review, replacing Wednesbury irrationality entirely. Consider constitutional principle, comparative perspectives, and practical implications.

Essential

• Paul Craig, 'Proportionality and Judicial Review: A UK Historical Perspective' in Judicial Review and the Constitution (ed. C Forsyth, 2000).
• Lord Steyn, 'Democracy, the Rule of Law and the Role of Judges' [2006] EHRLR 243.
• T.R.S. Allan, 'Human Rights and Judicial Review: A Critique of Due Deference' [2006] CLJ 671.

Highly recommended

• Mark Elliott, 'From Bifurcation to Calibration: Twin-Track Deference and the Culture of Justification' in The Scope and Intensity of Substantive Review (ed. Hayward, 2015).
• Jeffrey Jowell, 'Proportionality and Unreasonableness: Neither Merger nor Takeover' in The Human Rights Act: A Special Bulletin (Blackstone, 2000).
• Murray Hunt, 'Sovereignty's Blight: Why Contemporary Public Law Needs the Concept of Due Deference' in Public Law in a Multi-Layered Constitution (ed. Bamforth & Leyland, 2003).

Comparative and theoretical

• Janneke Gerards, 'How to Improve the Necessity Test of the European Court of Human Rights' (2013) 11 ICON 466.
• Jeff King, Judging Social Rights (CUP, 2012), ch 6 ('Rationality Review').
• Moshe Cohen-Eliya & Iddo Porat, Proportionality and Constitutional Culture (CUP, 2013).

Recent case comment

• Paul Daly, 'Wednesbury's Reason and Structure' [2011] PL 238.