| Council of Civil Service Unions v. Minister for the Civil Service [1985] AC 374 | Categories of judicial-review grounds (illegality, procedural impropriety, irrationality). | Illustrated breadth of possible challenges a defendant might raise. |
| Director of Public Prosecutions v. Head [1959] AC 83 | Defendant may rebut presumption of validity in criminal proceedings. | Cited to support availability of collateral challenge. |
| Anisminic Ltd. v. Foreign Compensation Commission [1969] 2 AC 147 | A legal error renders a decision a nullity; void/voidable distinction obsolete. | Used to reject limitation of collateral challenges to “facial” defects. |
| Reg. v. Hull University Visitor, Ex p. Page [1993] AC 682 | Ultra vires as foundation of judicial review. | Reinforced principle that unlawful acts have no legal effect. |
| O’Reilly v. Mackman [1983] 2 AC 237 | Procedural exclusivity for public-law claims. | Explained why collateral challenge is nevertheless permissible in criminal defence. |
| Ridge v. Baldwin [1964] AC 40 | Consequences of procedural unfairness. | Quoted to show that quashing renders prior acts legally ineffective. |
| F. Hoffmann-La Roche v. Secretary of State for Trade [1975] AC 295 | Presumption of validity pending successful challenge. | Clarified that presumption is evidential, not substantive. |
| Wandsworth LBC v. Winder [1985] AC 461 | Collateral challenge permissible in civil defence. | Analogy drawn to criminal context. |
| Associated Provincial Picture Houses v. Wednesbury Corp. [1948] 1 KB 223 | “Wednesbury” unreasonableness standard. | Referenced when discussing irrationality challenges. |
| Reg. v. Reading Crown Court, Ex p. Hutchinson [1988] QB 384 | Validity of byelaws may be tested in criminal courts. | Cited as authority supporting the Appellant’s position. |
| Kruse v. Johnson [1898] 2 QB 91 | Judicial scrutiny of byelaws. | Historical support for collateral review. |
| Bugg v. Director of Public Prosecutions [1993] QB 473 | Drew distinction between substantive and procedural invalidity. | House expressly overruled this distinction. |
| Smith v. East Elloe RDC [1956] AC 736 | Presumption that orders remain effective until quashed. | Discussed and distinguished. |
| London & Clydeside Estates v. Aberdeen DC [1980] 1 WLR 182 | Practical approach to procedural defects. | Considered but not followed. |
| Reg. v. Wicks [1998] AC 92 | Statutory context may limit collateral challenge. | Differentiated: unlike planning notices, the Transport Act had no limiting provision. |
| Quietlynn Ltd. v. Plymouth CC [1988] QB 114 | Narrow statutory regime limiting collateral challenge. | Explained contrast with present statutory framework. |
| Municipal Corp. of Toronto v. Virgo [1896] AC 88 | “Regulate” vs “prohibit.” | Considered but held not decisive in railway context. |
| Tarr v. Tarr [1973] AC 254 | Similar distinction between regulation and prohibition. | Discussed in analysing section 67. |
| Pyx Granite Co. v. Ministry of Housing [1960] AC 260 | Presumption against ousting access to courts. | Supported broad availability of collateral challenges. |
| Kirklees MBC v. Wickes Building Supplies [1993] AC 227 | No cross-undertaking required from public authority enforcing disputed law. | Cited when discussing Lord Diplock’s analysis of ultra vires. |