Parliament remains legally sovereign, but its power is increasingly constrained in practice.
Introduction
This essay will critically assess whether Parliament’s legal sovereignty endures in light of practical constraints, and whether framing this tension as a loss of sovereignty reflects a false dichotomy or a valid constitutional concern.
Parliament has long been regarded as the supreme legislative authority in the United Kingdom, with the theoretical ability to make or unmake any law. However, in recent decades, developments such as devolution, membership of international organisations, and the incorporation of human rights norms have raised questions about whether its sovereignty remains meaningful in practice. While some argue that these shifts erode parliamentary authority, others maintain that sovereignty continues to exist in law, even if political, legal, and constitutional factors increasingly shape its exercise. This essay will examine whether Parliament’s sovereignty has been undermined or merely evolved, and whether practical constraints constitute a genuine loss of constitutional power.
Foundations of Parliamentary Sovereignty
The origins of Parliament can be traced back to Magna Carta (1215), which introduced the principle that King John should consult a council of barons. This idea evolved into formal parliamentary consultation. The first English Parliament resembling a modern legislature was convened by Simon de Montfort in 1265, incorporating not only nobles and clergy but also commoners, marking the early beginnings of representative government in England. The Model Parliament of 1295, summoned by King Edward I, is often cited as the foundation of the modern bicameral structure. It included Lords Spiritual and Temporal (now the House of Lords), alongside elected knights and burgesses (the precursors to the House of Commons). The development of the Bill of Rights 1689 further entrenched parliamentary sovereignty, affirming that the monarchy could not rule without the consent of Parliament and requiring regular parliamentary sessions. This marked a key turning point in the evolution of the UK’s constitutional monarchy and the limitation of arbitrary royal power.
In his seminal 1885 work An Introduction to the Study of the Law of the Constitution, A.V. Dicey offered the most influential articulation of parliamentary sovereignty. Dicey argued that Parliament possesses the legal authority to make or unmake any law it chooses, and that no person or body—not even the courts—can override or set aside its legislation. This doctrine forms the orthodox view of UK constitutional law, asserting that parliamentary sovereignty is both absolute in law and central to the UK’s uncodified constitutional framework, regardless of political developments.
Today, Parliament, comprising the House of Commons, the House of Lords, and the Monarch, remains the supreme legislative authority in the United Kingdom. The House of Commons consists of 650 Members of Parliament (MPs), each elected to represent one of the United Kingdom's parliamentary constituencies across England, Wales, Scotland, and Northern Ireland. As of April 2025, the House of Lords comprises 829 members, predominantly life peers, along with a limited number of hereditary peers and Lords Spiritual. While the size and composition of the Lords may vary, their legislative role, alongside that of the elected Commons, remains a core component of parliamentary sovereignty, both in theory and in practice.
Constraints of Parliamentary Sovereignty
Over the centuries, the constitutional principle of parliamentary sovereignty has faced several constraints that have raised questions about its absoluteness and practical application. While these constraints have not entirely overridden the doctrine, they have challenged its supremacy in specific contexts.
Devolution: In 1998, Parliament enacted the Scotland Act 1998, the Government of Wales Act 1998, and the Northern Ireland Act 1998, establishing devolved legislatures with varying degrees of law-making power. While Parliament retains legal sovereignty and can, in theory, repeal or legislate on devolved matters, political realities make such actions highly controversial and practically constrained. This is reflected in the Sewel Convention, which holds that the UK Parliament will not normally legislate on devolved matters without the consent of the relevant devolved legislature. Although not legally binding, the convention was acknowledged in the Scotland Act 2016 and Wales Act 2017, reinforcing the political expectation that Westminster respects devolved autonomy. Furthermore, parts of the devolution legislation have been framed in terms of permanence, leading to what some describe as quasi-entrenchment. For example, the Scotland Act 2016 declares that the Scottish Parliament and Scottish Government are permanent institutions, and that they will not be abolished without a referendum of the Scottish people. While Parliament could legally repeal these provisions, such an action would be politically explosive and contrary to the spirit of the devolution settlement.
European Union (EU) Membership: By enacting the European Communities Act 1972, the UK gave domestic legal effect to EU law, meaning that in cases of conflict, EU law took precedence over domestic legislation, as affirmed in Factortame (No. 2) [1991] 1 AC 603. This was a significant limitation on parliamentary sovereignty, albeit one Parliament chose to accept, and later reversed by repealing the 1972 Act via the European Union (Withdrawal) Act 2018 following Brexit. The Brexit process reignited debates over the meaning of sovereignty, with many claiming that leaving the EU would "restore" parliamentary supremacy. However, the complexities of retained EU law and the continued influence of international obligations reveal that sovereignty remains subject to external pressures, even post-Brexit.
European Convention on Human Rights (ECHR): The UK became a party to the European Convention on Human Rights in 1951; however, this did not grant the Convention direct effect in domestic courts. The significant change came with the Human Rights Act 1998, which incorporated the Convention into UK law. Under this Act, UK courts must interpret legislation in a manner compatible with the Convention "so far as it is possible to do so" (s.3 HRA 1998). While courts cannot strike down primary legislation, they can issue a declaration of incompatibility. If domestic remedies are exhausted, individuals can still appeal to the European Court of Human Rights in Strasbourg.
Rule of Law: By the principle of partial separation of powers, a constitutional principle in the UK, the judiciary has suggested that there may be judicial limits to parliamentary control. In the case of Jackson v Attorney General [2005], Lord Steyn and Baroness Hale suggested that in extreme cases — such as if Parliament tried to abolish judicial review or the courts entirely — the judiciary might refuse to uphold such laws. While this is not a strict limit, it highlights a potential theoretical boundary rooted in the constitutional principle of the rule of law. As Lord Hope stated, “The rule of law, enforced by the courts, is the ultimate controlling factor on which our constitution is based.” A similar sentiment can be found in R (Evans) v Attorney General [2015] UKSC 21, where the judiciary resisted executive override of court decisions, reinforcing the growing assertiveness of the courts in upholding constitutional fundamentals.
Constitutional Statutes: In Thoburn v Sunderland City Council [2002] EWHC 195 (Admin), Laws LJ distinguished between ordinary statutes and "constitutional statutes," which cannot be impliedly repealed. Examples include the European Communities Act 1972 and the Human Rights Act 1998. Although this doctrine does not expressly limit Parliament’s power to repeal such laws, it does signal a shift in judicial thinking about the hierarchy of legislation and the durability of fundamental legal norms within the UK’s uncodified constitution.
Endurance of Legal Sovereignty
Despite the practical and political constraints outlined above, the orthodox legal position remains that Parliament retains ultimate legislative authority. This was affirmed in R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5, where the Supreme Court reiterated that only Parliament could change domestic law, reinforcing its role as the supreme law-making body. Even the European Communities Act 1972, which allowed EU law to take precedence, was enacted — and later repealed — by Parliament itself, underlining the fact that such constraints were self-imposed and revocable.
Similarly, devolution settlements, though politically sensitive, are grounded in statutes that Parliament can amend or repeal. The Scotland Act 2016, while asserting the “permanence” of the Scottish Parliament, does not legally prevent Westminster from legislating to the contrary. In theory, therefore, Parliament's legal sovereignty remains untouched — it can still make or unmake any law it chooses.
The Human Rights Act 1998 also reflects this principle. Courts may issue declarations of incompatibility under section 4 of the HRA, but they cannot strike down primary legislation. Parliament is not bound to amend or repeal incompatible laws and can legislate contrary to human rights protections if it so chooses. This maintains the constitutional orthodoxy that Parliament cannot bind its successors in law.
Even where the judiciary has hinted at potential limits — as in Jackson v Attorney General [2005] — such statements remain obiter dicta and do not overturn the foundational Diceyan principle. While Lord Steyn and others speculated about courts refusing to uphold specific extreme laws, there is no precedent for such a judicial veto. Miller further affirmed this by stating that "the legal power of the Crown to act on the international plane cannot be used to alter domestic law," reaffirming the supremacy of Parliament over both the executive and the courts in legal terms.
In sum, although parliamentary sovereignty is exercised within an increasingly complex constitutional environment, it has not been displaced in law. The doctrine has proven adaptable, continuing to underpin the UK’s uncodified constitution even in the face of globalisation, devolution, judicial activism, and Brexit.
Conclusion
Parliament remains legally sovereign, capable of making or unmaking any law it chooses. This core principle, rooted in Diceyan orthodoxy, continues to underpin the UK’s uncodified constitution and has been consistently reaffirmed by the courts. However, the practical exercise of this sovereignty is increasingly shaped by political, constitutional, and international realities. Devolution, human rights protections, Brexit, and judicial interpretations of the rule of law all place significant constraints on how Parliament can act without triggering constitutional or political backlash.
Yet to frame the relationship between legal and practical sovereignty as a binary, where the rise of one necessarily means the fall of the other, is to adopt a false dichotomy. The two are not mutually exclusive but instead reflect different dimensions of constitutional power: one rooted in legal theory, the other in political legitimacy and convention. Parliament’s sovereignty has not been lost; instead, it has evolved within a more pluralistic and accountable constitutional framework. The key challenge in the future is not whether sovereignty exists, but how it is exercised responsibly within a modern democracy.
Bibliography
Books
A V Dicey, An Introduction to the Study of the Law of the Constitution (Macmillan 1885)
Legislation
Bill of Rights 1689
European Communities Act 1972
European Union (Withdrawal) Act 2018
Government of Wales Act 1998
Human Rights Act 1998
Magna Carta 1215
Northern Ireland Act 1998
Scotland Act 1998
Scotland Act 2016
Wales Act 2017
Cases
Factortame Ltd v Secretary of State for Transport (No 2) [1991] 1 AC 603
Jackson v Attorney General [2005] UKHL 56
R (Evans) v Attorney General [2015] UKSC 21
R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5
Thoburn v Sunderland City Council [2002] EWHC 195 (Admin)