The Constitutional Function of Case Law
In a state with a codified constitution, the fundamental rules governing the exercise of public power are typically set out in a single, supreme written document. The United Kingdom, however, has no such codified constitution. Instead, the constitution is drawn from multiple sources, of which case law — that is, the body of judicial decisions developed through the common law and statutory interpretation — plays a particularly significant role. Case law shapes constitutional principles through three primary functions: establishing foundational principles through the common law, providing a mechanism to review the exercise of executive power through judicial review, and interpreting statute law in ways that carry constitutional significance.
The Common Law
The common law has, over centuries, generated a set of principles that now form part of the constitutional fabric of the United Kingdom. These principles constrain both the state and individuals, and continue to evolve through judicial decision-making.
Residual Freedom
One foundational principle is that of residual freedom: a citizen is free to do or say whatever he or she wishes, unless the law expressly prohibits the conduct in question. This contrasts with systems in which rights must be positively granted by the state. In Entick v Carrington [1765], government officials entered a private home and seized documents without any lawful warrant. The court held that this was unlawful because there was no legal authority for the search. The case established the principle that state power must have a clear legal foundation, and that individuals retain liberty in the absence of a legal prohibition.
The Requirement of a Legal Basis for State Action
Closely related to residual freedom is the constitutional requirement that state officials — including the police and other agents of the Crown — must be able to point to a legal basis for their actions. As confirmed in Entick v Carrington [1765], the absence of lawful authority renders an act of the state unlawful, regardless of the official's intention or the perceived public interest in undertaking it.
The Attribution of Judicial Functions to the Judiciary — Separation of Powers
The common law also establishes that judicial functions belong to the courts alone. In the Case of Prohibition (Prohibition del Roy) (1607), it was held that the Crown and government officials cannot intervene directly in legal disputes or exercise judicial powers. Legal controversies must be resolved by the judiciary through proper legal process. This principle reflects and reinforces the doctrine of the separation of powers: executive and judicial power are constitutionally distinct, and the courts guard their jurisdiction against encroachment.
Habeas Corpus and Individual Liberty
The ancient writ of habeas corpus is one of the most significant common law protections of individual liberty. It provides that a person detained by the state has the right to have the legality of that detention tested before a court. The state cannot hold an individual without lawful justification. This principle was dramatically illustrated in the Belmarsh Case [2005], in which the House of Lords considered the indefinite detention of terrorism suspects without charge or trial. The court held that such indefinite detention without judicial scrutiny of its legality was incompatible with fundamental rights and could not stand. The case demonstrated the judiciary's willingness to uphold constitutional liberties even against legislation enacted in the context of national security.
The Right to a Fair Hearing
The right to a fair hearing is a distinct and standalone common law constitutional principle, separate from the protections afforded by habeas corpus. It requires that before any adverse decision is made affecting an individual's rights or legitimate interests, that person must be given an opportunity to be heard. This principle is sometimes expressed through the Latin maxim audi alteram partem — hear the other side. It forms a cornerstone of natural justice and has been developed extensively through the common law, operating as a constitutional safeguard against arbitrary or one-sided decision-making by public bodies.
Parliamentary Supremacy
The common law also underpins the constitutional doctrine of parliamentary supremacy. Courts have consistently held that once an Act of Parliament has been duly enacted and entered upon the Parliamentary roll, it is not open to the courts to question its validity or strike it down. In Edinburgh & Dalkeith Railway v Wauchope (1842), it was confirmed that courts must apply Acts of Parliament as they stand. This position was reaffirmed in Pickin v British Railways Board [1974], in which the House of Lords made clear that it is not the function of the courts to examine what occurs in Parliament during the passage of legislation. Parliamentary supremacy is therefore itself a common law creation: the courts have recognised and enforced it through judicial decisions rather than through any higher written law.
Judicial Review of Executive Actions
The Constitutional Significance of Judicial Review
Although the courts do not have the power to review the constitutionality of Acts of Parliament — that power being reserved, in principle, to Parliament itself — case law serves the important constitutional function of reviewing the manner in which public bodies exercise the powers conferred upon them by Parliament. This process is known as judicial review. It is distinct from an appeal on the merits: judicial review does not ask whether the decision was the correct one, but whether it was made lawfully, by a body with the authority to make it, and through a fair process.
This function of case law can be contrasted with systems that have a dedicated constitutional court. In South Korea, for example, the Constitutional Court has the authority to strike down legislation that violates the Constitution. In the United Kingdom, no such institution exists; instead, the ordinary courts exercise a supervisory jurisdiction over executive action through judicial review, producing case law that regulates the state.
As illustrated in St Helen Council v Manchester Primary Care Trust [2008], the courts review whether public bodies have acted within the scope of the powers granted to them. The case demonstrates how judicial review operates as a practical mechanism for ensuring that public authorities remain accountable to the law.
Three Grounds of Judicial Review
English administrative law recognises three principal grounds upon which a decision of a public body may be challenged by way of judicial review.
Illegality — Ultra Vires
The first ground is illegality, often expressed through the Latin doctrine of ultra vires (beyond the powers). A decision is unlawful if the public body that made it lacked the legal authority to do so. Parliament confers powers on public bodies for specific purposes, and any exercise of those powers beyond their lawful scope is invalid. The courts will quash such a decision and, in appropriate circumstances, issue declarations or other remedies.
Procedural Fairness
The second ground is procedural fairness. Even where a public body has the legal authority to make a decision, it must exercise that authority through a procedurally fair process. This encompasses the requirements of natural justice: the decision-maker must not be biased (nemo judex in causa sua — no one may be a judge in their own cause), and the affected party must be given a fair opportunity to present their case (audi alteram partem). A failure of procedural fairness renders the decision susceptible to challenge regardless of whether the substantive outcome might have been correct.
Reasonableness and Proportionality
The third ground is reasonableness and proportionality. A decision that is so unreasonable that no reasonable public authority could have made it — the standard derived from administrative law and sometimes referred to as Wednesbury unreasonableness — may be struck down. In cases engaging human rights or EU law, a stricter standard of proportionality may apply: the decision must be no more restrictive of the claimant's rights than is necessary to achieve a legitimate aim. This ground of review allows courts to scrutinise the substance of a decision without substituting their own view for that of the decision-maker.
Interpretation of Statute
Judicial Interpretation of Constitutional Significance
The third primary constitutional function of case law is the interpretation of statute. When Parliament legislates, the words of a statute may be ambiguous, incomplete, or may come into conflict with other legal obligations. The courts must resolve such questions through interpretation, and the resulting case law can carry significant constitutional weight.
The Conflict Between an Act of Parliament and EU Law — Factortame
A dramatic example of the constitutional significance of statutory interpretation arose in Factortame (No 2) [1991]. At issue was a conflict between an Act of Parliament and directly effective EU law. The House of Lords held that, where domestic legislation was incompatible with EU law, the courts were required to suspend the operation of that Act insofar as it conflicted with Community law. This was a profound constitutional development: for the first time, a United Kingdom court disapplied an Act of Parliament in order to give effect to a superior legal obligation. The case demonstrated that the relationship between parliamentary sovereignty and European Community membership required courts to perform an active and constitutionally significant interpretive function.
Interpretation Under the Human Rights Act — Ghaidan v Mendoza
A further example of constitutionally significant interpretation is provided by Ghaidan v Mendoza [2004]. Under s 3 Human Rights Act 1998, courts are required, so far as is possible, to read and give effect to primary and subordinate legislation in a way that is compatible with the rights guaranteed by the European Convention on Human Rights. In Ghaidan v Mendoza [2004], the House of Lords applied this interpretive obligation to extend statutory protection to a same-sex partner, reading the relevant legislation in a manner compatible with the right to respect for private and family life under Article 8 of the Convention. The case illustrates that s 3 Human Rights Act 1998 confers on the courts a powerful interpretive tool that can alter the apparent meaning of legislation to bring it into line with Convention rights, without formally striking the legislation down.
The Hierarchy of Acts of Parliament — Thoburn v Sunderland City Council
Distinguishing Ordinary and Constitutional Statutes
A significant judicial development in statutory interpretation concerns the identification of a hierarchy of Acts of Parliament. In Thoburn v Sunderland City Council [2002], the court drew a distinction between ordinary statutes and what were termed "constitutional statutes". A constitutional statute is one that conditions the legal relationship between the citizen and the state in a fundamental way, or that enlarges or diminishes the scope of fundamental constitutional rights. Examples identified in the case include Magna Carta 1215, the Bill of Rights 1689, and the Human Rights Act 1998.
The Limitation of the Doctrine of Implied Repeal
The constitutional significance of this distinction lies in its effect on the doctrine of implied repeal. Under ordinary principles of parliamentary sovereignty, a later Act of Parliament impliedly repeals an earlier Act to the extent of any inconsistency between the two. However, the court in Thoburn v Sunderland City Council [2002] held that constitutional statutes are immune from implied repeal. They can be repealed or amended only by express provision; a later statute will not be taken to have overridden a constitutional statute simply because of a general or inadvertent inconsistency. This judicial recognition of a hierarchy within the statute book represents a significant constitutional development and demonstrates that the courts, through the exercise of interpretation, play an active role in shaping the structure of the United Kingdom constitution.