## Introduction

A.V. Dicey described Parliamentary sovereignty as the legal authority of Parliament to make or unmake any law, and the absence of any other body with the power to set aside an Act of Parliament. On that view, Parliament’s legislative reach is unlimited and its Acts are supreme.

Modern practice is more complicated. Membership of the European Union (and the route out of it), common law rules about constitutional statutes, devolution settlements, procedural limits around the Parliament Acts, and the rule of law have all pressed on the traditional picture. This guide sets out what Dicey said, what has changed, and what still stands today.

## What You’ll Learn

- The two limbs of Dicey’s theory and why they still matter
- How EU law supremacy operated through the European Communities Act 1972, and how Brexit altered the picture
- What “constitutional statutes” are and how they affect implied repeal
- How devolution and the Sewel Convention shape the political and legal position
- What the Parliament Acts show about “manner and form” limits
- The role of the rule of law and human rights in today’s constitution
- Key cases: Factortame, Thoburn, Jackson, AXA, and Miller
- Practical steps for analysing sovereignty questions in problem and essay answers

## Core Concepts

### Dicey’s classic formulation: two limbs

- Unlimited legislative competence: Parliament can legislate on any subject, in any terms.
- No rival authority: No court or other institution can disregard a valid Act of Parliament.

Read together, these limbs create a simple rule: enactment by the Queen-in-Parliament is the highest form of law in the UK. The challenge is to test how this rule fits with later developments.

### EU law then Brexit: supremacy by statute, then reset

- Entry point: The European Communities Act 1972 (ECA) brought EU law into UK law. Section 2(1) gave direct effect to EU obligations; section 2(4) told courts to read later Acts subject to EU obligations; section 3(1) steered courts to follow the Court of Justice.
- Supremacy in action: In the Factortame litigation, UK courts suspended and then disapplied parts of the Merchant Shipping Act 1988 that conflicted with EU law. The key move was not that EU law “overruled” Parliament on its own, but that Parliament had given EU law priority through the ECA.
- Parliamentary sovereignty affirmed: Section 18 of the European Union Act 2011 made clear that EU law had effect in the UK only by virtue of an Act of Parliament.
- Exit and after: The European Union (Withdrawal) Act 2018 repealed the ECA on exit day, preserved much EU-derived law as “retained EU law”, and limited the ongoing effect of supremacy. Later reforms, including the Retained EU Law (Revocation and Reform) Act 2023, further reduced any remaining supremacy effects. The upshot: supremacy of EU law in the UK was statutory and, through new statutes, it has largely been switched off.

### Constitutional statutes and implied repeal

- The rule in Thoburn v Sunderland City Council (2002): Some statutes are “constitutional” and are not repealed by implication. Repeal must be express. Examples often given include the Bill of Rights 1689, the ECA 1972, the Human Rights Act 1998 (HRA), and the devolution statutes.
- What changes: The common law still accepts that Parliament can repeal earlier Acts, but the courts expect clear wording to alter or remove constitutional protections. This is a shift in the standard approach to conflicting statutes, and it places a drafting burden on Parliament when it wishes to change constitutional rules.

### Devolution and the Sewel Convention

- Legal power: Devolved legislatures in Scotland, Wales, and Northern Ireland exercise powers granted by UK statutes. Westminster can, in law, legislate for devolved matters.
- Political restraint: The Sewel Convention states that Westminster will not normally legislate on devolved matters without consent. It is recognised in statute (e.g., Scotland Act 2016) but remains non-justiciable. The Supreme Court in Miller (2017) confirmed it is a political rule, not a legal limit.
- Practical effect: Legal sovereignty remains, but political realities make some uses of power costly.

### Manner and form after the Parliament Acts

- The Parliament Acts 1911 and 1949 allow certain Bills to become law without the House of Lords’ consent after delays and conditions. In Jackson (2005) the Law Lords upheld the 1949 Act and the Hunting Act 2004 made under the 1911 Act procedure.
- Lesson: Parliament can set procedures that change how future legislation is made. This is often called a “manner and form” limit. It is a procedural rule, not a limit on subject-matter. Parliament can still legislate, but it may need to use the right procedure.

### Rule of law and human rights

- Courts and the rule of law: In Jackson, Lord Hope stated that Parliamentary sovereignty “is no longer, if it ever was, absolute,” pointing to the rule of law as a judicially enforced principle. Courts have also interpreted ouster clauses narrowly (e.g., Anisminic, and more recently in Privacy International), showing a strong preference for legal accountability.
- Human Rights Act 1998: Courts can issue declarations of incompatibility under section 4, leaving Acts in force but flagging rights problems for Parliament to address. This respects legal sovereignty while inserting a strong constitutional signal.
- Overall: The rule of law frames how Parliament’s Acts are read and applied. It does not create a general power to strike down Acts but strengthens the expectation of clarity and fairness.

## Key Examples or Case Studies

### R (Factortame Ltd) v Secretary of State for Transport (No 2) [1991] 1 AC 603

- Context: Spanish-owned fishing companies challenged parts of the Merchant Shipping Act 1988 as inconsistent with EU law.
- What happened: UK courts granted interim relief and later disapplied the inconsistent provisions, following a ruling from Luxembourg.
- Why it matters: Shows EU law supremacy in the UK when given effect by the ECA 1972. Lord Bridge noted that any limit flowed from Parliament’s own statute.

### Thoburn v Sunderland City Council [2002] EWHC 195 (Admin)

- Context: “Metric Martyrs” case about imperial and metric measures and the interaction of statutes.
- What happened: Laws LJ recognised “constitutional statutes” that cannot be repealed by implication.
- Why it matters: Alters standard implied repeal rules and requires express words to change constitutional arrangements.

### R (Jackson) v Attorney General [2005] UKHL 56

- Context: Challenge to the validity of the Hunting Act 2004 made under the 1911/1949 Parliament Act procedure.
- What happened: The House of Lords upheld the 1949 Act and the Hunting Act.
- Why it matters: Confirms that Parliament can alter legislative procedure. Contains strong dicta on the rule of law and the status of Parliamentary sovereignty.

### AXA General Insurance Ltd v Lord Advocate [2011] UKSC 46

- Context: Challenge to an Act of the Scottish Parliament.
- What happened: The Supreme Court upheld the Act but made clear that devolved bodies are statutory and subject to judicial review principles.
- Why it matters: Emphasises that devolution is granted by Westminster statutes and operates within their limits.

### R (Miller) v Secretary of State for Exiting the EU [2017] UKSC 5

- Context: Could the Government trigger Article 50 without an Act of Parliament?
- What happened: The Supreme Court said no; an Act was required because leaving the EU would change domestic law and remove statutory rights.
- Why it matters: Reasserts that major constitutional changes require Parliament’s involvement and that the Sewel Convention is political, not legally enforceable.

## Practical Applications

- When faced with an Act vs EU measure issue:
  - Pre-Brexit: Check whether the ECA 1972 applied and whether EU law had direct effect and priority.
  - Post-Brexit: Identify if the rule is retained EU law or assimilated law, and whether any supremacy effect still applies to pre-2021 enactments under the Withdrawal Act regime.

- On implied repeal:
  - Ask if the earlier Act is “constitutional”. If so, look for express words altering or repealing it.
  - If not, apply standard implied repeal unless the court has signalled a special reading.

- On devolution problems:
  - Separate legal power (Westminster can legislate) from political convention (Sewel). Note any consent motion issues as political, not legal, unless the devolution statute makes something justiciable.

- On manner and form:
  - Check whether the Parliament Acts procedure or any special super-majority, referendum requirement, or other procedural step in a statute applies. If so, confirm it was followed.

- On the rule of law and rights:
  - Use the HRA framework: compatibility under section 3 if possible; otherwise, consider a section 4 declaration. Remember that a declaration does not affect validity.

- Exam and practice tip:
  - Structure answers by stating Dicey, identifying the modern pressure point (EU/Brexit, constitutional statute, devolution, manner and form, rule of law), citing a leading case, and concluding on whether any limit is legal, political, or procedural.

## Summary Checklist

- State Dicey’s two limbs: unlimited law-making power; no body can set aside an Act.
- EU law supremacy in the UK existed because of the ECA 1972; Brexit legislation has largely removed it.
- Thoburn created “constitutional statutes” that are not subject to implied repeal.
- Devolution changes politics, not legal sovereignty; Sewel is a political convention (Miller).
- Parliament can change legislative procedure (Jackson); these are manner-and-form rules.
- The rule of law influences interpretation and accountability; the HRA promotes rights-based review without striking down Acts.
- Always ask: Is the constraint legal, political, or procedural? What statute or case gives it force?

## Quick Reference

| Topic                     | Authority/Case                              | Key takeaway                                                                    |
| ------------------------- | ------------------------------------------- | ------------------------------------------------------------------------------- |
| Dicey’s two limbs         | Dicey, Introduction to the Study of the Law | Parliament can make/unmake any law; no rival authority to set aside an Act      |
| EU supremacy (pre-Brexit) | ECA 1972; Factortame (No 2) [1991]          | Supremacy operated via the ECA; courts could disapply conflicting UK law        |
| Brexit settlement         | EU (Withdrawal) Act 2018; REUL Act 2023     | ECA repealed; limited, shrinking supremacy effects for retained/assimilated law |
| Constitutional statutes   | Thoburn [2002]                              | No implied repeal of constitutional statutes; express words needed              |
| Devolution and Sewel      | Scotland Act 2016; Miller [2017]            | Sewel is political, not enforceable; legal sovereignty remains with Westminster |
| Manner and form           | Jackson [2005]; Parliament Acts 1911/1949   | Parliament may bind procedure; still free to legislate using proper process     |
| Rule of law and rights    | Jackson [2005]; HRA 1998                    | Courts uphold rule of law; HRA uses declarations rather than striking down      |


Dicey's Parliamentary Sovereignty Today