O’Reilly v Mackman [1983] UKHL 1 is a landmark decision in UK constitutional and administrative law, establishing the so-called “exclusivity principle”—that claims seeking to enforce rights protected by public law must generally be brought exclusively by way of judicial review. This decision has had a profound effect on procedural law, drawing a sharper line between public law and private law remedies, but also creating difficulties for litigants and prompting later cases to clarify or limit its scope.
Facts of O’Reilly v Mackman Case
The case arose from events following a riot in Hull prison, in which several convicted prisoners were implicated. As a disciplinary measure, the prison authorities decided that certain prisoners, including the claimants, would lose remission of their sentences.
The prisoners challenged this decision, arguing that it was null and void due to breaches of natural justice, drawing upon reasoning from R v Deputy Governor of Parkhurst Prison, ex parte St Germain [1979] QB 425. They claimed procedural unfairness in the disciplinary process and sought to have the decision quashed.
However, rather than proceeding through judicial review under Order 53 of the Rules of the Supreme Court (now largely contained in CPR Part 54), the prisoners brought their action by ordinary writ in the High Court, alleging breach of statutory duty and seeking declarations.
The defendants, representing the prison authorities, applied to strike out the claims on the ground that this was an abuse of process—public law decisions, they argued, could only be challenged via judicial review, which had strict time limits and required promptness.
Procedural History
- Court of Appeal: The Court of Appeal, led by Lord Denning MR, held that it was indeed an abuse of process to bring a claim in ordinary proceedings when the matter was purely one of public law. Lord Denning distinguished public law (governing the relationship between individuals and public authorities) from private law (governing relations between individuals). Historically, public law was enforced via prerogative writs such as certiorari, mandamus, and prohibition, which were limited in their scope. Over time, private law remedies like damages, declarations, and injunctions had been made available in certain public law contexts, but Lord Denning stressed that where a claim was purely public law in nature, it should proceed by judicial review to maintain procedural safeguards.
- House of Lords: The House of Lords upheld this reasoning and struck out the prisoners’ claims. This created a clear procedural rule that pure public law challenges must be brought through judicial review.
O’Reilly v Mackman Judgement of the House of Lords
The lead speech was given by Lord Diplock, whose words have since been frequently cited as the foundation of the exclusivity principle.
Key Holdings
- Judicial review is the only appropriate method of challenging decisions of public authorities when the claim is solely about public law rights.
- The court has jurisdiction to grant declarations and other remedies in public law cases, but Order 53 exists to protect public authorities from delayed or unmeritorious claims.
- Where public bodies act in private law contexts (e.g., in contracts, torts, or property disputes), they are subject to ordinary private law proceedings.
- Attempting to challenge a public law decision through an ordinary action is, as a general rule, an abuse of process.
Lord Diplock’s Principle
Lord Diplock articulated the policy behind the decision in clear terms:
“Since all remedies for infringements of rights protected by public law can be obtained upon an application for judicial review, as can also remedies for infringements of rights under private law if such infringements should also be involved, it would in my view as a general rule be contrary to public policy, and as such an abuse of the process of the court, to permit a person seeking to establish that a decision of a public authority infringed rights to which he was entitled to protection under public law to proceed by way of an ordinary action and by this means to evade the provisions of Order 53 for the protection of such authorities.”
In other words, judicial review is a specialised procedural route designed for public law challenges, with built-in safeguards like permission requirements and time limits to ensure public bodies are not hindered by stale or frivolous claims. Allowing ordinary actions in such circumstances would undermine these protections.
Public vs Private Law Distinction
In O’Reilly v Mackman [1983] UKHL 1, the court reinforced the conceptual distinction between:
- Public law: Governs the relationship between the state (or public authorities) and individuals; its breach is addressed via judicial review.
- Private law: Governs relationships between private individuals or entities; breaches are remedied via ordinary proceedings.
The case acknowledged that public authorities may sometimes operate in the private law sphere—such as entering contracts or committing torts—and in those situations, the ordinary private law route is appropriate.
Procedural Safeguards in Judicial Review
The judgement strongly emphasised the importance of Order 53 safeguards, now largely replicated in CPR Part 54:
- Promptness in bringing claims.
- Time limit of three months from the date of the decision (unless exceptional circumstances justify delay).
- Permission stage to screen out hopeless claims.
- Restriction to certain remedies (quashing orders, prohibiting orders, mandatory orders, declarations, and injunctions).
These safeguards serve to protect public bodies from excessive litigation and to ensure that administrative decisions are not subject to prolonged uncertainty.
Constitutional Implications
The exclusivity principle established in O’Reilly v Mackman [1983] UKHL 1 has been criticised for clashing with the Diceyan conception of the rule of law, which insists that the same legal rules and procedures should apply to the state as to private individuals. Dicey rejected the idea of separate administrative law courts and procedures, arguing for a single unified legal system. By requiring a distinct procedural route for public law claims, the House of Lords effectively created a special track for cases against public bodies—something Dicey would have opposed.
Conclusion
O’Reilly v Mackman [1983] UKHL 1 remains one of the most influential cases in UK administrative law. By cementing the exclusivity principle, it ensured that public law disputes are channelled through a specialised procedural route designed for their resolution. While the ruling brought clarity and protection for public bodies, it also created procedural complexity for claimants, especially in mixed cases. Later decisions such as Roy have introduced nuance, but the essential principle laid down by Lord Diplock continues to guide the procedural framework for challenging public authority decisions. The case is both a cornerstone of modern judicial review and a continuing source of debate about the balance between procedural efficiency and substantive justice.
