The classic definition comes from A.V. Dicey (1885), who described it as having three main elements:

1. Parliament can make or unmake any law.
   There are no substantive limits on what Parliament can legislate about. It can pass laws on any subject, from taxation to constitutional reform.

2. No Parliament can bind a future Parliament.
   Each Parliament is free to change or repeal any previous Act. For example, one Parliament cannot make an “entrenched” law that later Parliaments cannot alter.

3. No person or body can override or question an Act of Parliament.
   Once a law is enacted, the courts must apply it. Judges cannot declare an Act invalid or unconstitutional.

Together, these principles establish that statute law is the highest source of legal authority in the UK.

Parliament consists of the House of Commons, the House of Lords, and the Monarch. In practice, the elected Commons dominates the law-making process, and once a Bill receives Royal Assent, it becomes binding law. Courts must apply Acts of Parliament even if they conflict with fundamental principles or prior decisions.

Example:

• In Cheney v Conn [1968], a taxpayer argued that a Finance Act was unlawful because it funded nuclear weapons, contrary to international law. The court rejected this, confirming that an Act of Parliament overrides other sources of law.

Although Parliament remains legally sovereign, its supremacy has been limited in practice by several constitutional developments.

a) The European Union (Historical Impact)

While the UK was a member of the EU, EU law took precedence over domestic law.
In Factortame (No. 2) [1991], the House of Lords disapplied parts of the Merchant Shipping Act 1988 because it conflicted with EU law, an unprecedented restriction on parliamentary supremacy.
After Brexit, the European Union (Withdrawal) Act 2018 restored full legislative sovereignty.

b) The Human Rights Act 1998

The Human Rights Act (HRA) requires courts to interpret legislation, where possible, in line with the European Convention on Human Rights (ECHR).
If that is impossible, judges may issue a declaration of incompatibility under s.4 HRA, but they cannot strike down the law. Parliament retains the final say.

c) Devolution

The Scotland Act 1998, Government of Wales Act 2006, and Northern Ireland Act 1998 grant devolved legislatures powers over certain areas.
However, these powers exist only because Parliament granted them, in theory, Westminster can still legislate for the entire UK (s.28(7) Scotland Act 1998).

d) The Rule of Law and Judicial Review

Although Parliament is supreme, the courts interpret and apply its statutes. In cases such as Jackson v Attorney General [2005], senior judges questioned whether there might be “fundamental constitutional principles” that even Parliament could not abolish (e.g. the rule of law or judicial review).
This remains controversial, sovereignty in law still belongs to Parliament, but political and moral limits constrain its use.