Parliamentary sovereignty

A fundamental principle of the United Kingdom’s constitution is that the UK Parliament is sovereign. This means that Parliament has “the right to make or unmake any law whatever” and that “no person or body” has “a right to override or set aside the legislation of Parliament”, according to the constitutional scholar A. V. Dicey.

This principle, which is also known as parliamentary supremacy, is recognised in the European Union (Withdrawal Agreement) Act 2020. In the absence of a codified constitution, the principle provides the UK with a recognised internal hierarchy of laws. It also governs the relationship between the legislature (Parliament), the executive (the government) and the courts.

Despite being a core rule of the UK constitution, the origins, nature and extent of parliamentary sovereignty are complex and sometimes disputed. Judges and constitutional scholars have, especially in the 20th and 21st centuries, disagreed with one another regarding the ultimate authority for parliamentary sovereignty and about whether it is unlimited or constrained by other constitutional rules or norms.

The orthodox account of parliamentary sovereignty

The “orthodox” account of parliamentary sovereignty is most closely associated with A. V. Dicey’s book, An Introduction to the Study of the Law of the Constitution, which was first published in 1885.

Dicey defined Parliament as a tripartite body comprising the Monarch, the House of Lords and the House of Commons. Sovereignty, in this context, meant it possessed the legal authority to make or unmake any law, and that no other institution could override its primary legislation (acts of Parliament). On the same basis, Parliament could not entrench legislation against repeal by future Parliaments (“bind its successors”).

This account was subsequently defended by the legal scholar Sir William Wade throughout the 20th century.

The history of parliamentary sovereignty

The idea of parliamentary sovereignty developed gradually. In medieval England, monarchs ruled via the Curia Regis, a council comprising nobles and clergy. Over time, this evolved into the Parliament of England, which gained increasing authority over taxation and legislation. By the Tudor period, Parliament was used to legitimise royal decisions, including religious reforms under Henry VIII and Elizabeth I.

The Glorious Revolution of 1688, when Parliament helped depose James II of England, marked a turning point. The Bill of Rights (England) and the Claim of Right (Scotland) established that monarchs could only govern with the consent of the then separate Parliaments of England and Scotland. This affirmed the principle that law could only be made by the Crown-in-Parliament, and not by the Monarch acting alone.

Following the Anglo-Scottish Union of 1707 and the British-Irish Union of 1801, concepts of parliamentary sovereignty were extended to the new parliaments of Great Britain (1707 to 1801) and of the United Kingdom (1801 to present). However, Lord Cooper (the then Lord President of the Court of Session in Scotland) observed in 1953 that “the principle of unlimited sovereignty of Parliament is a distinctively English principle and has no counterpart in Scottish constitutional law”.

Legal and political conceptions of sovereignty

Dicey distinguished between legal and political sovereignty. Legal sovereignty refers to the power to make laws without legal limitation. Political sovereignty acknowledges that Parliaments are chosen by the electorate, and that their laws are only practically effective if voters consented to them. Dicey acknowledged that Parliament’s legal authority does not depend on its democratic credentials, although its political legitimacy may do.

For example, the Septennial Act 1715 extended the maximum duration of Parliament from three to seven years. Dicey noted that while such a move might be politically controversial, it would be legally valid and enforceable by the courts.

Parliament’s ability to make or unmake any law

Under the orthodox account, Parliament’s legislative powers are substantively unlimited. It can override legal rights, make retrospective laws (affecting the legality of actions in the past as well as in the future), breach international obligations, extend its own duration or even abolish itself. Dicey and the constitutional lawyer Sir Ivor Jennings both emphasised that Parliament could legislate on any subject, and that no law was immune from repeal.

There is no special process for constitutional law-making in the UK. All acts of Parliament are equal in status, and newer acts take precedence over older in cases of conflict. This contrasts with the situation in countries which have codified constitutions, where constitutional amendments require special procedures and may be subject to judicial review.

Under the Parliament Acts 1911 and 1949 it is possible for a bill to be presented for Royal Assent without the agreement of the House of Lords, provided that certain conditions are met. This change was seen by some as a departure from Dicey’s notion of sovereignty conferred upon a tripartite body.

Parliament cannot bind its successors

Another central tenet of the orthodox account is that no Parliament can bind its successors, meaning that any Parliament can repeal or amend a law passed by a previous Parliament. Dicey argued that any attempt to create immutable legislation would be legally ineffective, as a future Parliament could repeal it by passing another act of Parliament.

Historical examples support this view. The Protestant Religion and Presbyterian Church Act 1707 (passed by the pre-union Parliament of Scotland) was intended to secure the position of the Church of Scotland after the Anglo-Scottish Union and declared itself a fundamental and unchangeable condition of that union. However, the Universities (Scotland) Act 1853 repealed parts of it. Similarly, the Union with Ireland Act 1800 declared that the union of the Churches of England and Ireland “shall remain in full force for ever,” but the Irish Church Act 1869 disestablished the Church of Ireland.

Dicey distinguished between Parliament binding its successors and surrendering its sovereignty. He argued that Parliament could abdicate its sovereignty by dissolving itself or transferring authority to another body, such as the Church Assembly (later the General Synod), the devolved Parliament of Northern Ireland or certain legislatures in the British Empire following the Statute of Westminster, 1931.

Judicial enforcement of acts of Parliament

Dicey maintained that courts must implement acts of Parliament and could not strike them down. This is unlike subordinate legislation (also known as secondary or delegated legislation, such as statutory instruments) which the courts can nullify. This principle has for several centuries been consistently upheld in UK constitutional law. Judges may interpret primary legislation, but they cannot invalidate it on moral or constitutional grounds.

This distinguishes the UK from most jurisdictions with codified and entrenched constitutions, such as the United States, where courts can strike down legislation which violates its constitution. In the UK, courts must apply acts of Parliament even if they conflict with common law, delegated legislation or international obligations.

The role of the common law

The source of parliamentary sovereignty has been disputed. Dicey and Wade argued that it is a political fact. Others, including Ivor Jennings, have suggested that it may instead be a legal rule of the common law.

If parliamentary sovereignty is a common law rule, it could theoretically be modified by the courts acting alone. However, this view is controversial and raises questions about the legitimacy of judicial authority to alter fundamental constitutional principles.

Alternative theories of sovereignty

Some scholars have proposed alternatives to Dicey’s orthodox account. The “manner and form” theory, developed by Jennings and later refined by Michael Gordon, suggests that Parliament can impose procedural or formal requirements on future legislation without limiting its substantive law-making power.

Under this theory, Parliament could require that certain laws be passed with a supermajority (for example, a two-thirds majority) or following a referendum. These requirements would not constrain Parliament’s ability to legislate on any subject but would regulate the process by which laws are made. For example, under the Fixed-term Parliaments Act 2011 (now repealed), an early dissolution of Parliament required a two thirds majority decision in the Commons.

However, Jeffrey Goldsworthy has argued that even procedural requirements may be incompatible with parliamentary sovereignty if they make legislation practically impossible. He has rejected referendum requirements and any supermajority threshold as inconsistent with Parliament retaining its substantive power to legislate.

Challenges to parliamentary sovereignty

Parliamentary sovereignty has faced several challenges. The territorial challenge argues that the 1707 Acts of Union (which unified Scotland and England to form “Great Britain”) included provisions which limited Parliament’s authority. However, courts have generally upheld the principle that later acts of Parliament override earlier ones, even if the earlier acts contain entrenching language (such as “forever after be United”).

Common law constitutionalism, meanwhile, suggests that the rule of law, rather than parliamentary sovereignty, is the fundamental principle of the UK constitution. Some judges and scholars have argued that courts should have the power to invalidate legislation which violates fundamental human rights or constitutional norms. According to Lord Hope, while the UK constitution might be “dominated by the sovereignty of Parliament,” this is “no longer, if it ever was, absolute” (PDF).

The UK’s membership of the European Union (1973-2020) also raised questions about parliamentary sovereignty. The European Communities Act 1972 gave effect to EU law in the UK, and courts applied EU law even when it conflicted with domestic legislation. The Factortame case is often cited as an example of a court setting aside an act of the UK Parliament in favour of EU law. However, this was based on the UK’s voluntary acceptance of EU obligations. Parliament also exercised its sovereignty in triggering the UK’s withdrawal from the EU in 2017 and repealing the 1972 act.

The Human Rights Act and judicial interpretation

The Human Rights Act 1998 requires courts to interpret legislation in a way that is compatible with the European Convention on Human Rights “so far as it is possible to do so”. This has led to debates about whether courts are departing from the intention of the UK Parliament in decisions based on the convention.

However, similar interpretive presumptions have long existed in common law, and the 1998 act does not give courts the power to invalidate legislation. Under section 4, a court can only make a declaration of incompatibility. It is then up to Parliament to take remedial legislative action.

Devolution and sovereignty

The establishment of devolved legislatures in Scotland, Wales and Northern Ireland in the late 1990s added another nuance to concepts of parliamentary sovereignty.

While the UK Parliament retains the legal authority to legislate on any matter, including those which are devolved in Scotland and Wales or transferred in Northern Ireland, the Sewel Convention seeks to limit the exercise of that power.

The Scotland Act 1998 (as amended), for example, includes a provision that the Scottish Parliament cannot be abolished except following a referendum in Scotland. However, this provision could be repealed by an act of Parliament.

The previous Parliament of Northern Ireland, which existed between 1921 and 1973 was abolished (during the period known as The Troubles) via primary legislation at Westminster.