UK Constitutional Law & Judicial Precedent Guide 2026

1. Constitutional Statutes vs Ordinary Statutes

The distinction between **constitutional statutes** and ordinary statutes is associated particularly with *Thoburn v Sunderland City Council* [2002] EWHC 195 (Admin). Laws LJ suggested that the common law recognises a category of statutes with special constitutional status. Ordinary statutes are generally subject to the traditional doctrine of implied repeal: where a later Act is inconsistent with an earlier Act, the later legislation may prevail to the extent of the inconsistency. Constitutional statutes receive different treatment. They are not normally subject to implied repeal, so a later Act must use express words or wording so specific that the legislative intention to repeal or fundamentally alter the constitutional statute is unmistakable. This does **not** mean that constitutional statutes are permanently entrenched or superior to Parliament. Parliament remains legally capable of expressly repealing or amending them. The distinction is principally a rule of statutory interpretation and constitutional law concerning how Parliament's intention is identified.

2. Parliamentary Sovereignty and Constitutional Statutes

The constitutional-statute doctrine must be understood alongside **Parliamentary Sovereignty**. The special treatment of constitutional statutes does not create a higher legislature or permanently prevent Parliament from changing constitutional law. Instead, it modifies the normal interpretive assumption that a later inconsistent Act automatically repeals an earlier one by implication. This distinction was significant in *Thoburn* because Laws LJ described constitutional statutes as occupying a special category. The doctrine preserves Parliament's ability to legislate while requiring clearer evidence of parliamentary intention where fundamental constitutional legislation is being repealed or significantly altered. The concept therefore provides a limited form of constitutional protection without creating an entrenched written constitution. It is important not to describe constitutional statutes as statutes that Parliament 'cannot repeal'. Parliament can repeal them; the issue is whether the repeal is sufficiently clear.

3. Thoburn v Sunderland City Council

*Thoburn v Sunderland City Council* [2002] EWHC 195 (Admin) is a leading constitutional-law authority associated with the distinction between ordinary and constitutional statutes. The case concerned the interaction between the Weights and Measures Act 1985 and legislation giving domestic effect to European Community obligations. Laws LJ stated that ordinary statutes may be impliedly repealed, whereas constitutional statutes may not. He identified constitutional statutes as statutes that condition the legal relationship between citizen and State in some general, overarching manner or enlarge or diminish the scope of fundamental constitutional rights. The judgment is important because it recognised a constitutional hierarchy for purposes of statutory interpretation while expressly preserving legislative supremacy. It did not establish a supreme written constitution or give courts a general power to invalidate Acts of Parliament.

4. Implied Repeal: How the Doctrine Works

**Implied repeal** is the principle that a later Act can displace an earlier inconsistent Act even where the later Act does not expressly state that the earlier provision is repealed. The doctrine rests on the idea that the later expression of Parliament's will takes priority where two Acts cannot coherently operate together. However, constitutional statutes are treated differently. Erskine May records the principle associated with *Thoburn*: ordinary statutes may be impliedly repealed, while constitutional statutes are not subject to ordinary implied repeal. For constitutional legislation, the court looks for clear evidence of the legislature's actual intention to repeal or abrogate the relevant constitutional rule. This is why it is inaccurate to say either that 'all Acts can always be impliedly repealed' or that 'constitutional statutes can never be repealed'. The legally accurate position lies between those two extremes.

5. Dicey's Rule of Law

A.V. Dicey's classic account of the **Rule of Law** identified three central ideas. First, there should be the absolute supremacy or predominance of regular law over arbitrary power. Second, there should be equality before the law, meaning that officials and citizens are subject to the ordinary law administered by the ordinary courts. Third, in Dicey's historical account, constitutional principles were closely connected with rights developed and protected through the ordinary law and courts rather than through a single codified constitutional text. Modern UK constitutional law has developed beyond Dicey's nineteenth-century formulation. Contemporary understandings of the Rule of Law also encompass legality, accessibility and clarity of law, procedural fairness, access to justice, judicial independence and effective legal accountability of public authorities. Dicey's formulation remains important historically and academically, but it should not be presented as a complete statement of every modern Rule of Law requirement.

6. Royal Prerogative and Judicial Review

The **Royal Prerogative** consists of historic executive powers of the Crown. In modern government, many prerogative powers are exercised by ministers on behalf of the Crown or formally by the Sovereign on ministerial advice. The existence of a prerogative power does not automatically make its exercise immune from judicial review. Courts can determine the legal scope of prerogative powers and, depending on the nature of the power and the issue, may review whether an exercise of prerogative is lawful. The constitutional significance of the prerogative is particularly clear in the Miller litigation. *Miller I* concerned the Government's proposed notification under Article 50 of the Treaty on European Union. *Miller II* concerned advice to prorogue Parliament. The cases addressed different constitutional questions and should not be collapsed into a single proposition.

7. Miller I: Article 50 and Parliamentary Sovereignty

In **R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5**, the Supreme Court considered whether the Government could use the Royal Prerogative to notify the European Union of the UK's intention to withdraw under Article 50 TEU without prior authorisation from an Act of Parliament. The Supreme Court held that the Government could not trigger Article 50 solely through prerogative power because doing so would inevitably affect domestic legal rights created through Parliament's legislation. Parliamentary authorisation was therefore required. Miller I is an important example of the relationship between Parliamentary Sovereignty and executive prerogative. It did not hold that the courts could strike down an Act of Parliament. Instead, it limited executive action where using prerogative power would undermine rights created by Parliament.

8. Miller II: Prorogation of Parliament

In **R (Miller) v The Prime Minister [2019] UKSC 41**, commonly called Miller II, the Supreme Court considered whether the Prime Minister's advice to the Queen to prorogue Parliament was justiciable and lawful. The Court held that the issue was justiciable and formulated a constitutional standard: a decision to exercise the prerogative power to prorogue Parliament would be unlawful if it had the effect of frustrating or preventing, without reasonable justification, the ability of Parliament to carry out its constitutional functions as legislature and as the body responsible for supervising the executive. The Court concluded that the advice given to the Queen was unlawful because it had the relevant effect without reasonable justification. The prorogation was therefore void and of no legal effect. Miller II is a major authority on the judicial review of prerogative power and the constitutional relationship between Parliament and executive government.

9. Constitutional Conventions

**Constitutional conventions** are political rules and practices governing how constitutional actors are expected to behave. They are distinct from legal rules. A convention can be constitutionally important without being directly enforceable by a court as an independent cause of action. Examples include conventions concerning ministerial responsibility, the relationship between the Government and Parliament and the exercise of certain formal powers of the Crown. Conventions can evolve as political circumstances change, and their precise content may sometimes be disputed. Courts can nevertheless recognise and discuss conventions when deciding legal questions. The important distinction is that recognition of a convention does not necessarily mean that a court will enforce the convention itself as if it were ordinary law.

10. The Ministerial Code

The **Ministerial Code** sets out standards of conduct expected of UK Government ministers and explains how ministers should discharge their duties. It is an important part of the framework of ministerial standards and executive accountability. The Code is not equivalent to an Act of Parliament. It is an executive constitutional instrument setting standards for ministers, and its operation is connected with the Prime Minister's constitutional and political responsibility for ministerial appointments and conduct. The official GOV.UK publication was updated on 29 June 2026. The Ministerial Code should therefore be distinguished from both legislation and constitutional conventions. It can reflect constitutional principles and expectations without automatically creating an ordinary statutory cause of action in court.

11. The Salisbury Convention

The **Salisbury-Addison Convention** concerns the relationship between the House of Lords and government legislation implementing manifesto commitments. In its modern formulation, the Lords does not normally block a government manifesto bill at second reading, does not use 'wrecking amendments' to defeat the manifesto intention, and returns the bill to the House of Commons in reasonable time so that the Commons can consider amendments. The convention developed from an understanding reached between Viscount Cranborne and Viscount Addison during the Labour Government of 1945-51. Its application can become more complicated where there is a minority government or coalition because questions can arise about whether a manifesto provides the relevant electoral mandate. The Salisbury Convention is a political convention, not a statutory rule giving the courts power to order the House of Lords to pass a bill.

12. Parliamentary Sovereignty and the Modern Constitution

Parliamentary Sovereignty remains a central doctrine of UK constitutional law, but its operation must be considered alongside the Rule of Law, judicial review, constitutional statutes, devolution, human-rights legislation and constitutional conventions. The orthodox doctrine means that courts generally cannot invalidate a properly enacted Act of the UK Parliament simply because they regard it as unconstitutional. However, courts can control unlawful executive action, interpret legislation, recognise constitutional principles and determine whether devolved legislation falls within statutory competence. The modern constitution is therefore not accurately described as either 'Parliament can do anything' or 'courts can override Parliament'. The constitutional relationship is more precise: Parliament has extensive legislative authority, while executive government and public authorities remain subject to law and judicial control.

13. Constitutional Law After Brexit

Brexit provides an important modern example of constitutional change. The European Union (Withdrawal) Act 2018 repealed the European Communities Act 1972 and established a new domestic framework for retained EU law, which was subsequently modified by later legislation including the Retained EU Law (Revocation and Reform) Act 2023. The Brexit litigation also illustrates the continuing importance of Parliamentary Sovereignty and judicial review. Miller I required parliamentary authorisation before Article 50 could be triggered, while later legislation supplied that authorisation. The courts did not themselves decide whether the UK should leave the EU; they decided constitutional questions about the lawful allocation of powers between Parliament and the executive. Brexit therefore demonstrates how major constitutional change can occur through ordinary legislation within an uncodified constitutional system.

14. Why the UK Constitution Is Not Simply 'Unwritten'

The description **'unwritten constitution'** can be misleading. The UK constitution contains extensive written legislation and judicial decisions. The more accurate description is **uncodified constitution** because there is no single constitutional document that comprehensively sets out the fundamental rules of government. This distinction matters when explaining constitutional statutes, the Human Rights Act 1998, devolution legislation, judicial review and the Supreme Court. Each forms part of a written legal framework even though the UK does not have one entrenched constitutional text.

Frequently Asked Questions (6 Interlinked FAQs)

Official Government & Judicial References

• • UK Supreme Court — R (Miller) v Prime Minister [2019] UKSC 41 (Miller II Prorogation Judgment)
• • UK Supreme Court — R (Miller) v Secretary of State for Exiting EU [2017] UKSC 5 (Miller I Judgment)
• • High Court of Justice — Thoburn v Sunderland City Council [2002] EWHC 195 (Admin) (Constitutional Statutes)
• • Cabinet Office — Official Ministerial Code & Government Conventions

Related UK Legal & Constitutional Guides