Parliamentary Sovereignty and Its Limits

Parliamentary sovereignty is the foundational principle of the UK constitution. It determines where ultimate legal authority lies and shapes every debate about the distribution of power in the British political system. This lesson examines the meaning, scope, and contemporary challenges to parliamentary sovereignty.

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A.V. Dicey and Parliamentary Sovereignty

The classic definition of parliamentary sovereignty comes from A.V. Dicey in An Introduction to the Study of the Law of the Constitution (1885). Dicey identified three key elements:

1. Parliament can make or unmake any law — There is no subject on which Parliament cannot legislate. It can pass any law it chooses, no matter how radical.
2. No body can override or set aside an Act of Parliament — The courts cannot strike down primary legislation. Unlike the US Supreme Court, UK courts have no power of constitutional review over Acts of Parliament.
3. No Parliament can bind its successors — Each new Parliament is free to repeal or amend any law passed by a previous Parliament. This means there can be no permanently entrenched legislation.

Key Definition: Parliamentary sovereignty means that the Westminster Parliament is the supreme legal authority in the UK, and its Acts cannot be challenged by any other body.

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Legal Sovereignty vs Political Sovereignty

It is essential to distinguish between legal sovereignty (where the law says power lies) and political sovereignty (where power lies in practice):

Legal Sovereignty	Political Sovereignty
Parliament is the supreme legal authority	In practice, power may lie with the electorate, the PM, the media, or international bodies
The courts must apply Acts of Parliament	The government (Executive) dominates Parliament through its majority
No law is beyond Parliament's reach	Political realities constrain what Parliament will legislate

Example: Legally, Parliament could abolish the Scottish Parliament. Politically, this would be unthinkable — it would provoke a constitutional crisis and likely a push for Scottish independence. The Sewel Convention reflects this political reality by stating that Westminster will not normally legislate on devolved matters without the consent of the devolved legislature.

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Challenges and Limits to Parliamentary Sovereignty

While Dicey's doctrine remains the legal orthodoxy, several developments have challenged or complicated parliamentary sovereignty in practice:

1. EU Membership (1973–2020)

The European Communities Act 1972 gave EU law supremacy over UK law in areas of EU competence. The landmark Factortame case (1990) saw UK courts disapply an Act of Parliament (the Merchant Shipping Act 1988) because it conflicted with EU law. This was described as a constitutional revolution because it appeared to breach Dicey's principle that no body can override an Act of Parliament.

Counter-argument: Parliament voluntarily chose to accept EU law supremacy through the 1972 Act, and it could (and did) repeal that Act by leaving the EU. Therefore, sovereignty was pooled, not lost. Brexit demonstrated that parliamentary sovereignty was ultimately preserved.

2. Devolution

The Scotland Act 1998, Government of Wales Act 1998, and Northern Ireland Act 1998 transferred significant legislative powers to devolved bodies. In theory, Westminster retains sovereignty and could legislate on devolved matters or even abolish the devolved parliaments. In practice, the Sewel Convention and political reality make this almost impossible.

The Scotland Act 2016 recognised the permanence of the Scottish Parliament and government and placed the Sewel Convention on a statutory footing. However, the Supreme Court ruled in Miller I (2017) that this statutory recognition did not make the convention legally enforceable.

3. The Human Rights Act 1998 (HRA)

The HRA incorporated the European Convention on Human Rights (ECHR) into UK law. Under Section 3, courts must interpret legislation compatibly with Convention rights "so far as it is possible to do so." Under Section 4, if a court finds an Act of Parliament incompatible with a Convention right, it can issue a declaration of incompatibility — but it cannot strike the Act down. Parliament then decides whether to amend the law.