## Introduction

A.V. Dicey famously described parliamentary sovereignty as the principle that Parliament can make or unmake any law, and no person or body can override its Acts. He also maintained that Parliament cannot bind its successors. For many years this was taught as an absolute rule.

Modern constitutional practice shows a more layered picture. EU membership (before Brexit), the rise of constitutional statutes, devolution, the Parliament Acts procedure, and the rule of law and human rights have all shaped how sovereignty operates in real cases. Legally, Parliament remains supreme, but its freedom is framed by statute, judicial technique, and political realities. This guide sets out the core ideas, landmark cases, and practical steps to apply them with confidence.

## What You’ll Learn

- Dicey’s classic two-limb account of parliamentary sovereignty
- How the European Communities Act 1972 gave EU law priority in UK courts, and what changed after Brexit
- The idea of constitutional statutes and limits on implied repeal from Thoburn
- Devolution, the Sewel Convention, and what Miller says about legal vs political limits
- The Parliament Acts (1911 and 1949), manner and form, and the House of Lords’ judgment in Jackson
- The rule of law, the Human Rights Act 1998, and the principle of legality (Simms)
- How to analyse exam and practice problems using these doctrines

## Core Concepts

### Dicey’s classic formulation

Dicey’s account is often summarised in two limbs:

- Unlimited legislative competence: Parliament can legislate on any subject.
- No binding successors: No Parliament can limit the legislative power of a future Parliament.

Courts must give effect to Acts of Parliament. If a statute is clear, judges apply it even if it conflicts with common law or older statutes. On this model, constraints are political, not legal.

Two technical points often raised with Dicey:

- Parliament can change any rule about how laws are made, but cannot entrench future Parliaments in a way that removes their law‑making power altogether.
- If a later Act conflicts with an earlier one, the later Act prevails (implied repeal), unless the courts treat the earlier Act as special in some way (see “constitutional statutes” below).

### EU law and the European Communities Act 1972

Before Brexit, the European Communities Act 1972 (ECA 1972) brought EU law into domestic law and gave it priority where there was a clash.

Key features:

- Section 2(1): EU law rights became part of UK law without further enactment.
- Section 2(2): Ministers could make secondary legislation to comply with EU obligations (a “Henry VIII” style power because it can amend primary legislation).
- Section 2(4): UK statutes were to be construed subject to EU obligations.
- Section 3: UK courts would follow rulings of the Court of Justice.

In Factortame (No 2) [1991] 1 AC 603, UK courts disapplied parts of the Merchant Shipping Act 1988 that conflicted with EU law. The House of Lords treated this as a consequence of Parliament’s choice in 1972. The European Union Act 2011, s18, later confirmed that EU law took effect in the UK by virtue of Acts of Parliament.

Brexit changed the legal setting but not the historical lesson. The ECA 1972 was repealed by the European Union (Withdrawal) Act 2018, which created the “retained EU law” scheme. The status of retained EU law has since been adjusted (for example by the Retained EU Law (Revocation and Reform) Act 2023). For exam and practice purposes, Factortame remains the leading example of Parliament choosing to give priority to a body of external law through clear legislation.

### Constitutional statutes and limits on implied repeal

In Thoburn v Sunderland City Council [2002] EWHC 195 (Admin), Laws LJ identified “constitutional statutes” (such as the ECA 1972 and the Human Rights Act 1998) that are not subject to implied repeal. The court will not treat a later, general Act as silently cutting down a constitutional statute. Any change must be express.

This does not make such statutes entrenched. Parliament can amend or repeal them, but it must use clear words. The practical effect is a form of hierarchy in interpretation: constitutional statutes get special treatment unless Parliament unmistakably decides otherwise.

### Devolution and the Sewel Convention

The Scotland Act 1998, Government of Wales Acts (now Wales Act 2017), and the Northern Ireland Act 1998 created devolved legislatures with defined competences. Formally, the UK Parliament can still legislate for any part of the UK.

The Sewel Convention reflects political practice: Westminster will not normally legislate on devolved matters without the consent of the relevant devolved legislature. Section 28(8) of the Scotland Act 1998 recognises this. In AXA General Insurance v Lord Advocate [2011] UKSC 46, the Supreme Court stressed that the Scottish Parliament is not sovereign in the Diceyan sense, but that devolution is a significant constitutional development.

In Miller [2017] UKSC 5, the Court held that s28(8) is a recognition of a political convention, not a legally enforceable rule. Parliament remains legally free to legislate, but doing so without consent can carry serious political costs.

### Manner and form and the Parliament Acts

The Parliament Acts 1911 and 1949 altered the route by which statutes can be enacted, allowing a Bill to become law without the Lords in certain conditions. In R (Jackson) v Attorney General [2005] UKHL 56, the House of Lords confirmed the validity of the 1949 Act and of the use of the Parliament Acts procedure for the Hunting Act 2004.

Jackson is often discussed as an example of “manner and form”: Parliament can set procedural requirements for making law. Future Parliaments must follow those valid procedures unless they are changed by a later Act. Some judges in Jackson made strong comments about sovereignty and the rule of law. The upshot: Parliament can redesign its own legislative procedure, and courts will police whether those procedures have been properly used.

One firm limit remains: the 1911 Act itself bars using the procedure to extend the life of Parliament beyond five years.

### Rule of law, the HRA 1998 and the principle of legality

The rule of law is a core constitutional value. Several senior judges have suggested that sovereignty is shaped by it. In Jackson, Lord Hope said parliamentary sovereignty is not absolute and that the rule of law is the “ultimate controlling factor” in our constitution.

The Human Rights Act 1998 gives courts two main tools:

- Section 3: So far as possible, legislation must be read compatibly with Convention rights.
- Section 4: If not possible, a court can issue a declaration of incompatibility. The Act remains valid unless and until Parliament changes it.

The principle of legality (ex p Simms [2000] 2 AC 115) means Parliament must use clear words if it intends to override basic common law rights. Courts will not infer such an intention from general or ambiguous language. This is a rule of interpretation, not a power to strike down Acts, but it shapes how far statutes are read.

EU law also produced rights‑based limits before Brexit. For example, in R (Davis) v Secretary of State for the Home Department [2015] EWHC 2092 (Admin), the High Court applied EU law standards on data retention when assessing a UK statute. Post‑Brexit, that source has receded, but the broader pattern of rights-sensitive interpretation remains strong.

## Key Examples or Case Studies

### Factortame (No 2) [1991] 1 AC 603

- Context: Spanish-owned fishing vessels challenged parts of the Merchant Shipping Act 1988.
- Holding: UK courts disapplied conflicting provisions because EU law, via the ECA 1972, had priority.
- Why it matters: Shows Parliament can, by clear statute, give another legal order priority in domestic courts. Often presented as “sovereignty by consent”.

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

- Context: The “metric martyrs” case about trading standards and EU-related regulations.
- Holding: Identified constitutional statutes that are not subject to implied repeal; changes require express words.
- Why it matters: Introduces a hierarchy of statutes in interpretation, softening Dicey’s vision of all Acts being equal in effect.

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

- Context: Challenge to the validity of the Hunting Act 2004 enacted under the Parliament Acts procedure.
- Holding: The 1949 Act and the procedure were valid. Strong judicial comments about limits on sovereignty were made obiter.
- Why it matters: Confirms Parliament can set “manner and form” rules for law‑making and that the courts will police compliance.

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

- Context: Could the Government trigger Article 50 without an Act of Parliament? What about devolved consent?
- Holding: An Act was required to trigger Article 50. The Sewel Convention is not legally enforceable.
- Why it matters: Reinforces legal control over major constitutional steps and clarifies the political (not legal) nature of Sewel.

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

- Context: Challenge to an Act of the Scottish Parliament.
- Holding: The Scottish Parliament is not sovereign; its Acts are reviewable for competence, but courts show respect for its role.
- Why it matters: Highlights the distinct status of devolved bodies and the continuing legal sovereignty of Westminster.

### R v Secretary of State for the Home Department, ex p Simms [2000] 2 AC 115

- Context: Prisoners’ rights to communicate with journalists.
- Holding: Basic rights cannot be overridden by general words; clear words are needed.
- Why it matters: The principle of legality shapes statutory interpretation and sets a high bar for curtailing fundamental rights.

### R (Davis) v Secretary of State for the Home Department [2015] EWHC 2092 (Admin)

- Context: Challenge to the Data Retention and Investigatory Powers Act 2014.
- Holding: The court applied EU law standards when assessing the statute, leading to findings of incompatibility.
- Why it matters: Illustrates how EU law influenced domestic outcomes pre‑Brexit.

## Practical Applications

- Start with Dicey: Set out the two limbs (unlimited competence; no binding successors). Then test the scenario against modern qualifications.
- Identify the type of limit:
  - Legal and court‑enforced (e.g., Factortame via ECA 1972; Thoburn’s express repeal rule; HRA s3/4; Parliament Acts procedure).
  - Political or conventional (e.g., Sewel Convention).
- EU law questions:
  - Pre‑Brexit facts: apply ECA 1972 framework and Factortame.
  - Post‑Brexit facts: consider retained EU law and any changes to its status (check the latest provisions).
- Constitutional statutes:
  - Ask whether the statute engaged (HRA 1998, devolution Acts, ECA 1972 when in force) is “constitutional”.
  - If yes, look for clear express words before treating it as altered.
- Devolution:
  - Check the competence of the devolved legislature.
  - Treat Sewel as a political constraint unless a specific statutory requirement is justiciable.
- Parliament Acts:
  - If a challenge concerns validity of an Act, ask whether the correct procedure was used.
  - Remember Parliament cannot extend its own life via the Parliament Acts route.
- Human rights and legality:
  - Apply HRA s3 strong interpretive duty before considering s4.
  - Use Simms: clear words are needed to curtail basic rights.
- Structure for essays and problems:
  1. State Dicey.
  2. Apply any statutory frameworks (ECA/HRA/devolution Acts).
  3. Discuss case law (Factortame, Thoburn, Jackson, Miller, Simms).
  4. Distinguish legal from political limits.
  5. Conclude on whether sovereignty is affected in form, in practice, or both.

Common pitfalls to avoid:

- Saying courts can strike down Acts. They cannot; they can disapply in specific contexts (e.g., under ECA pre‑Brexit) or issue declarations (HRA).
- Treating Sewel as a legal bar. It is recognised in statute but remains a convention.
- Ignoring Brexit’s effect on EU law supremacy post‑2018/2020.
- Forgetting that “constitutional statutes” can still be repealed expressly.

## Summary Checklist

- Dicey’s rule: Parliament can make or unmake any law; cannot bind successors.
- Factortame: EU priority pre‑Brexit came from ECA 1972; a choice by Parliament.
- EU Act 2011 s18: EU law took effect via Acts of Parliament.
- Thoburn: constitutional statutes are not subject to implied repeal.
- Devolution: significant in practice; Sewel is political (Miller).
- Parliament Acts: valid “manner and form” procedure (Jackson).
- HRA 1998: s3 interpretive duty; s4 declarations; no strike‑down power.
- Principle of legality (Simms): clear words required to override basic rights.
- Post‑Brexit: check retained EU law status and amendments.
- Always separate legal limits (courts enforce) from political limits (conventions and consequences).

## Quick Reference

| Topic                     | Authority                               | Key takeaway                                                       |
| ------------------------- | --------------------------------------- | ------------------------------------------------------------------ |
| Dicey’s formulation       | Dicey, Introduction to the Constitution | Parliament can legislate on any matter; cannot bind successors     |
| EU priority pre‑Brexit    | ECA 1972; Factortame [1991]             | Courts disapplied conflicting Acts due to Parliament’s 1972 choice |
| Status of EU law in UK    | EU Act 2011 s18                         | EU law had effect only through Acts of Parliament                  |
| Constitutional statutes   | Thoburn [2002]                          | No implied repeal; express wording needed to change them           |
| Devolution & Sewel        | Scotland Act 1998 s28(8); Miller [2017] | Sewel is recognised but not legally enforceable                    |
| Parliament Acts procedure | Jackson [2005]                          | Valid “manner and form” route; courts police its use               |
| Human rights tools        | HRA 1998 ss3–4; Simms [2000]            | Strong interpretation first; declarations if not possible          |

Dicey on Parliamentary Sovereignty