Parliamentary Sovereignty Lecture

The implication of Parliamentary Sovereignty is that the Westminster Parliament is legally entitled to pass, amend, or repeal any law that it wishes. An Act normally requires the approval of both Houses and Royal Assent. Under the Parliament Acts certain public bills can become law without the Lords’ approval. The courts have no general power to invalidate an Act of the UK Parliament. Parliamentary Sovereignty is a statement of law, not of politics; politically Parliament may not be able to pass every law it wishes. The Monarch in Parliament is in this sense sovereign or supreme, having the supreme or ultimate law-making power in the UK. Sovereignty raises several important questions: what is the basis of Parliamentary Sovereignty, can Parliament really pass any law and can a present Parliament prevent its successors from enacting certain future legislation?

A. The History of Parliamentary Sovereignty

The recognition by the Monarch and the courts of Parliament's legislative supremacy was developed in a series of cases during the 17th century.

• In The Case of Proclamations [1611] 12 Co Rep 74; 77 ER 1352, Chief Justice Coke held that the King has only the prerogative that the law allows and cannot change the law or create a new offence by proclamation.
• However, in R v Hampden (1637) 3 State Tr 825 a majority upheld Charles I's demand for ship money without parliamentary consent. Parliament subsequently declared the levy and the judgment unlawful. In Godden v Hales (1686) 11 St Tr 1166 the issue was different. The court upheld James II's power to dispense with the Test Act in the case of an individual officer.
• In Dr Bonham's Case (1610) 8 Co Rep 114, Chief Justice Coke argued that it was the common law as developed by the judiciary which was the ultimate legal protection for the people. Coke states (at 118) "...when an Act of Parliament is against common right and reason, or repugnant, or impossible to be performed, the common law will control it, and adjudge such an Act to be void". The case concerned the College of Physicians sitting in judgement on an offence from which it stood to gain. Coke's words are not a modern power to invalidate an Act.
• In Day v Savadge (1614) Hob 85, Hobart CJ suggested that an Act of Parliament would be invalid if it were 'made against natural equity', such as a law making a man judge in his own cause. This was an observation rather than a decision striking down an Act.

The Glorious Revolution of 1688 and the constitutional settlement of 1689 changed the nature of Parliamentary supremacy. Charles I asserted his exclusive power to rule and to legislate, a power which he claimed derived from God. Years later, when the throne was offered to William of Orange and Mary, subject to their recognition of Parliament's legislative supremacy, this was enshrined within the Bill of Rights 1689, which rejected the Crown's claimed power to suspend laws. Article 9 specifically protects speech, debates and proceedings in Parliament. The Crown could not levy taxation by prerogative without a parliamentary grant [e.g. Bowles v Bank of England [1913] 1 Ch 57]. The powers of Parliament and Parliamentary privilege are set out in the Bill of Rights 1689, but they have been developed over a period of time since then in an incremental manner.

• British Railways Board v Pickin [1974] AC 765, Lord Reid stated that since the Revolution of 1688, the law of God, or of nature, or of natural justice could not overrule an Act of Parliament.

More recently, Parliament has been confirmed to be supreme, or sovereign.

M v Home Office and another [1994] 1 AC 377, Lord Templeman at 395 rejected the suggestion that the executive obeyed the law as a matter of grace. A minister could be bound by a court order.

K Swinton, 'Challenging the Validity of an Act of Parliament: the effect of enrolment and parliamentary privilege' [1976] 14(2) Osgoode Hall Law Journal 345, 363; the principle of Parliamentary Sovereignty evolved through the struggles between Parliament and the Crown in the 17th century. Parliamentary legislative authority was established by the end of the 15th century, but it was not clear whether such Acts were still subject to review by the common law or natural law. The Glorious Revolution of 1688 confirmed that the royal prerogative, which is founded on the common law, could not overrule Acts of Parliament. On this account, parliamentary sovereignty is recognised by the common law.

H.L.A Hart: The 'rule of recognition' is binding because it is accepted by judges and officials; its origin being in politics and ideology. Speculative writings by Lord Woolf, Lord Justice Sedley and Lord Justice Laws challenge the notion that Parliament could make any law and the courts will respect it. They raise the question whether Parliamentary sovereignty is legally constrained by the Rule of Law and by fundamental rights. No general judicial power to invalidate an Act of the UK Parliament on those grounds has been established.

B. Sources of Parliamentary Sovereignty

Jennings (I. Jennings, The Law and the Constitution (5th edn, University of London Press, 1959)) asserts that Parliamentary Supremacy is rooted in the legal rule that courts accept legislation that Parliament enacts as law. Whereas Dicey (A.V. Dicey, Introduction to the Study of the Law of the Constitution, 1885) maintained that Parliamentary Sovereignty is contained within the common law.

In fact, the sources of Parliamentary Sovereignty are to be found within the UK constitution, which in the absence of a single codified constitution is to be found in:

• statute law;
• common law;
• constitutional conventions;
• some other category of norm?

i. Statute

The basic rules of parliamentary supremacy are not found in statute. Several commentators have explained why this is not possible.

Sir John Salmond, Jurisprudence (12th edn, Sweet and Maxwell, 1966: 111) stated that "no statute can confer this power [parliamentary supremacy] upon Parliament, for this would be to assume and act on the very power that is to be conferred". Parliament is incapable of conferring sovereignty upon itself via statute.

Eric Barendt, An Introduction to Constitutional Law (OUP, 1998: 87) "Parliament could declare .. that it is legally sovereign and [able] to enact any legislation it likes. But [this] would not add anything to its legislative capacity. Parliament can hardly confer constitutional authority on itself by its own enactment".

Parliament can acknowledge its law-making power in legislation, but not confer it; e.g. s.28(7) Scotland Act 1998. Section 28(8) recognises the Sewel convention that Westminster will not normally legislate on devolved matters without the Scottish Parliament's consent. As Miller [2017] UKSC 5 confirmed, this is a political convention, not a legal veto.

ii. Common Law

Eric Barendt, An Introduction to Constitutional Law (OUP, 1998: 86) discusses the source of the UK's Parliamentary legislative authority and the scope of that power. It is the courts that must decide whether Parliamentary authority prevails over inconsistent rules of law. "It is therefore the courts, rather than Parliament itself, which have formulated the principle which is the corner-stone of the uncodified constitution of the United Kingdom".

iii. A constitutional convention?

This idea can be rejected on the basis that constitutional conventions are not justiciable and enforceable by the courts, whereas the courts can apply the parliamentary supremacy rules.

iv. Another category of norm?

Several writers have argued that parliamentary supremacy is in a class of its own. For example:

H.W.R. Wade, 'The Basis of Legal Sovereignty' [1955] CLJ 172: "[I]f no statute can establish the rule that the courts obey Acts of Parliament, similarly no statute can alter or abolish that rule. This rule is above and beyond the reach of statute [...] because it is itself the source of the authority of statute. This puts it in a class by itself among rules of common law, and the apparent paradox that it is unalterable by Parliament turns out to be a truism" .. "the relationship between the courts of law and Parliament is first and foremost a political reality".

C. Theories of Parliamentary Sovereignty

Parliamentary sovereignty is said to be the power that has been given to that body by the people to enable it to make the law so as to permit a stable form of government, one that is capable of providing a social contract with the people that provides them with safety and security.

A.V. Dicey, Introduction to the Study of the Law of the Constitution, 1885, identified three main principles of Parliamentary Supremacy:

1. Parliament is the supreme law-making body and can enact laws on any subject matter.
2. Parliament cannot bind its successors.
3. No court of law (or other body) can question the validity of Parliament's enactments.

Considering each in turn:

Principle 1: Parliament can enact any law on any subject matter it chooses

Parliament can enact laws on any subject matter, but politically this may not be possible. For example, it might be politically impossible to enact legislation which requires women and men to own property as a precondition of voting. Parliament has enacted retrospective legislation which affects acts which occurred prior to the passage of the Act. Article 7 European Convention on Human Rights and Fundamental Freedoms 1950 (ECHR) prohibits conviction for conduct that was not criminal under national or international law when it occurred, and the retrospective imposition of a heavier penalty. Parliament has also enacted legislation which operates extraterritorially, such as the War Crimes Act 1991 and the Criminal Justice and Immigration Act 2008.

A series of cases decided towards the end of the British Empire illustrate some practical limitations on Parliament's legislative competence:

British Coal Corporation v R [1935] AC 500, the Privy Council affirmed the impact of the Statute of Westminster 1931 which allowed Canada to abolish appeals to the Privy Council in criminal cases. Sections 2 to 6 applied to Australia on adoption rather than automatically. Section 4 of the Statute of Westminster 1931 provided that a future Westminster Act would not extend to a Dominion as part of its law unless the Act expressly declared that the Dominion had requested and consented to it.

Madzimbamuto v Lardner-Burke [1969] 1 AC 645: if Parliament chose to pass a law which is morally, politically or otherwise improper, the courts cannot hold the Act of Parliament to be invalid. The case involved the Southern Rhodesia Act 1965, which asserted the Westminster Parliament's legislative supremacy over Southern Rhodesia, despite Ian Smith's unilateral declaration of independence. Although Parliament can enact any law, it does not mean that citizens of the territory could be forced to acknowledge its supremacy in practice.

Some authors argue that certain areas are beyond the reach of the Westminster Parliament. In MacCormick v Lord Advocate (1953) SC 396, the Lord President indicated that parliamentary sovereignty in its traditional formulation was English, not Scottish. He argued that the Acts of Union 1707 provided for amendment or repeal of certain provisions, but not all. Practically, any change in the relationship between Scotland and England would require significant political negotiation. His observations did not invalidate an Act of the UK Parliament. In Singh v Secretary of State for the Home Department [2025] CSIH 4 the Inner House rejected a challenge to a Westminster provision restricting judicial review of certain Upper Tribunal decisions in Scotland.

Principle 2: May Parliament Bind Subsequent Parliaments?

Entrenchment

Jennings and Heuston consider that Parliament may entrench legislation under some circumstances so as to bind future parliaments. Heuston's understanding of parliamentary supremacy makes it possible for Parliament to change the way that legislation is enacted and to provide for legislation to be entrenched.

I. Jennings, The Law and the Constitution (5th edn, University of London Press, 1959: 152–3) challenges Dicey's theory. He argues that supremacy is a more accurate description of Parliament's legislative competence. He suggests that Parliamentary Supremacy is a legal concept which describes the relationship between Parliament and the courts. He states that this 'means that the courts will always recognise as law the rules which Parliament makes as legislation' (1959: 149). Later he states: '... Legal sovereignty is merely a name indicating that the legislature has for the time being power to make laws of any kind in the manner prescribed by law' (Jennings, 1959: 152).

R.F.V. Heuston, Essays in Constitutional Law (2nd edn, Stevens and Sons, 1964: 6–7) asserted that a new view of sovereignty had overtaken Dicey's theory. Heuston argues that:

1. Sovereignty is a legal concept: rules which identify the sovereign and decide its formulation and functions are logically prior to it.
2. The rules which govern the composition, procedure and area of powers of the sovereign legislature can be distinguished.
3. The courts can question the validity of an Act on its composition or its procedure, but not on the area of powers of the legislature.
4. This jurisdiction is exercisable before or after the Royal Assent.

On the orthodox view there is no substantive domestic legal limit on the laws that the UK Parliament may enact. Where, then, do constraints come from? Is Parliament capable of entrenching legislation, requiring that the legislation can neither be repealed nor amended? Various scholars have offered theories in answer to this question. Three options have been presented:

1. Parliamentary sovereignty as a constitutional fixture.
2. Parliament is capable of controlling certain aspects of the legislative process.
3. Unintended constraints exist upon parliamentary authority.

The doctrines of express and implied repeal are used when the courts are faced with two Acts of Parliament on the same subject matter that contradict each other. Some writers argue that entrenchment is not possible.

Entrenchment clauses and prospective formulae are statutory provisions which attempt to protect an Act of Parliament from amendment or repeal. An entrenchment clause requires that a special procedure be adopted in order to amend or repeal a specific statute, such as a referendum or a two-thirds majority in favour. Section 1 of the Northern Ireland Act 1998 requires the consent of a majority of those voting in a poll before Northern Ireland can cease to be part of the UK and form part of a united Ireland. This is a condition for changing Northern Ireland's status. It does not expressly require a referendum to amend s.1 itself.

Prospective formulae seek to protect a statute from repeal or amendment by stating that its provisions prevail over those of subsequent statutes. A historic example of such a provision existed within s.2(4) European Communities Act 1972, which provided that any enactment shall be construed to have effect subject to the preceding provisions of s.2, including the rule giving effect to directly effective Community law. The European Communities Act 1972 was repealed by s.1 European Union (Withdrawal) Act 2018 upon the UK's departure from the EU on 31 January 2020, but its effect was saved with modifications until the transition period ended on 31 December 2020 (see section G below).

Express or Implied Repeal

In 1955, H.W.R. Wade, 'The Basis of Legal Sovereignty' [1955] CLJ 172 argued that it was impossible for Parliament to entrench legislation because the courts are constitutionally required to give effect to the most recent expression of parliamentary intention whenever two Acts conflict.

• First, it is always possible for Parliament to enact legislation that leads to some or all of an earlier Act being repealed [express repeal].
• Second, if a later ordinary statute is irreconcilable with an earlier ordinary statute, it is still the courts' constitutional duty to disregard the older law in relation to the inconsistency between the two [implied repeal]. This was endorsed in Ellen Street Estates Ltd v Minister of Health [1934] 1 KB 590.

In Ellen Street Estates Ltd v Minister of Health [1934] 1 KB 590, Maugham LJ stated:

The legislature cannot, according to our constitution, bind itself as to the form of subsequent legislation, and it is impossible for Parliament to enact that in a subsequent statute dealing with the same subject-matter there can be no implied repeal. If in a subsequent Act Parliament chooses to make it plain that the earlier statute is being to some extent repealed, effect must be given to that intention just because it is the will of the Legislature.

When two ordinary statutes cannot be reconciled the more recent legislation is preferred over the older legislation. Wade argued that both express and implied repeal cannot be displaced. For example, in Wade's view a section that states 'This Act may not be repealed' would have no effect. Absolute entrenchment is then impossible. If an Act states that it cannot be repealed unless some condition is first fulfilled, and Parliament were then to expressly or impliedly repeal the earlier Act, in Wade's view the latter Act would still repeal the earlier Act, whether or not the condition stipulated in the earlier Act had been fulfilled. This means contingent entrenchment is also impossible.

How can Wade assert (i) that Parliament is sovereign, but (ii) it is incapable of entrenching legislation? The answer lies in the distinction between self-embracing and continuing sovereignty. A Parliament with self-embracing sovereignty has the power to limit or destroy its own sovereignty. Wade asserts that the UK Parliament has continuing sovereignty, which cannot be destroyed, and thus Parliament cannot entrench legislation.

Principle 3: No court or body can question the legal validity of an Act of Parliament

Principle 1 means there is no area on which Parliament cannot legislate and Principle 3 means that courts recognise a validly enacted Act of the UK Parliament as law. A question about whether a bill became an Act under the Parliament Acts procedure is distinct from a challenge to its substantive validity.

Manuel v Attorney General [1983] Ch 77 – the case confirms that it is the duty of the court to obey and apply every Act of the UK Parliament, and the court cannot hold an Act to be ultra vires. The courts do not investigate Parliament's internal proceedings to impeach an enrolled Act. They can, however, construe the statutory conditions of the Parliament Acts, as in Jackson below. Courts may, however, invalidate delegated legislation which is deemed to be ultra vires.

Stockdale v Hansard [1839] 9 Ad & E 1; 112 ER 1112 – a resolution of only the House of Commons cannot make or alter the law; the Commons could not create a privilege against defamation proceedings simply by asserting it in a resolution.

Parliament does recognise some limits on its supremacy, but it is arguable that these are political limitations. In the UK's 'dualist' system, a treaty can bind the UK internationally without changing domestic law. Legislation is needed where the treaty requires a change to domestic law. International law does not render a contradictory domestic law void. Cheney v Conn [1968] 1 All ER 779 asserts the hierarchical superiority of Acts of Parliament even over international law. The courts operate the presumption that Parliament does not intend to legislate in contradiction with international law, so where possible they will interpret the statute to give a meaning consistent with the international provision.

D. Continuing Sovereignty

Parliament has the authority to make the law under the constitution. The UK does not have a codified written constitution; Wade considered that the Glorious Revolution gave Parliament the authority to make the law. England experienced a serious tension between the King and Parliament in the 17th century, with the two vying for constitutional primacy. On Wade's account, the basis of Parliament's authority to make law consists of a political agreement made in the 17th century between the monarchy, Parliament and the courts. The settlement came to be understood to mean that Parliament could make any law and that the courts would recognise Acts of Parliament as valid laws.

Wade states that this agreement is not a legal rule in any conventional sense – Parliament did not legislate to afford itself authority. It is rather 'the ultimate political fact upon which the whole system of legislation hangs': H.W.R. Wade, 'The Basis of Legal Sovereignty' [1955] CLJ 172, 188.

H.L.A. Hart refers to this as the 'rule of recognition': '[i]n the day-to-day life of a legal system its rule of recognition is very seldom expressly formulated', rather 'its existence is shown' ... 'in the way in which particular rules are identified': H.L.A. Hart, The Concept of Law (OUP, 1961: 98). According to the 'rule of recognition' the ordinary requirements for an Act and the treatment of later inconsistent legislation can be distinguished as follows:

1. House of Commons approval;
2. House of Lords approval (other than where the Parliament Acts apply);
3. Obtained the Royal Assent;
4. A later inconsistent Act can amend or repeal an earlier Act. This affects its continuing operation, not whether it was validly enacted.

In the UK, Wade claims that Parliament cannot entrench legislation. In many countries the fundamental rule of legal validity is to be found within a written constitution; but in the UK it exists only in Wade's 'political fact'. This rule of recognition or political fact cannot be amended by Parliament, since it is not law, and hence beyond Parliament's legislative reach.

Can Parliament amend its own Constitution?

If Parliament can pass, repeal or amend any law that it likes, it is able to amend the constitution. Relevant case law suggests that it is able to do so for particular purposes.

In Jackson v Attorney General [2005] UKHL 56; [2006] 1 AC 262, the House of Lords had to determine the validity of the Parliament Act 1949, which amended the Parliament Act 1911. The 1949 Act was passed without the consent of the House of Lords in accordance with the procedure stipulated in section 2 of the 1911 Act. If the 1949 Act were invalid, the Hunting Act 2004 (which had been passed under the Parliament Acts procedure) would also be invalid. The House of Lords held that there is no constitutional principle or principle of statutory interpretation which prevents a legislature from amending its own constitution in accordance with the provisions of a statute which empowers it to do so. Both Acts were upheld. For non-money bills, s.2 as amended requires passage by the Commons in two successive sessions and at least one year between the second reading in the first and passage by the Commons in the second. It excludes a bill extending the maximum duration of Parliament beyond five years. Section 1 provides a separate one-month procedure for certified money bills.

E. The Human Rights Act 1998

The Human Rights Act 1998 (HRA) remains in force in the UK and has significant implications for the supremacy of Parliament.

• s.2 HRA obliges courts to take account of decisions of the European Court of Human Rights (ECtHR) when reviewing cases that deal with Convention rights. Following the Supreme Court's decision in R (AB) v Secretary of State for Justice [2021] UKSC 28, the UK courts will follow ECtHR jurisprudence where there is a clear and constant line of authority, but are not bound to do so and may depart from Strasbourg case law where there are good reasons.
• s.3 HRA generally obliges the courts to interpret legislation, so far as it is possible to do so, in a manner which is compatible with Convention rights as defined in s.1 HRA, drawn from the European Convention on Human Rights 1950 (ECHR).
• s.4 HRA gives the courts listed in s.4(5), including the High Court in England and Wales, the Court of Session in Scotland and the High Court in Northern Ireland, jurisdiction to issue a declaration of incompatibility where primary legislation cannot be read compatibly with a Convention right, or where primary legislation prevents the removal of an incompatibility in subordinate legislation. A declaration of incompatibility does not affect the validity, continuing operation or enforcement of the provision; the government is not legally bound to amend incompatible legislation, although in practice it usually does. Once a declaration is final, s.10 permits a minister to make a remedial order where there are compelling reasons to do so.

The courts cannot invalidate an Act of the UK Parliament for incompatibility with a Convention right. Devolved legislation is subject to the limits of legislative competence in the devolution statutes.

F. European Union Law and its Historical Implications for Parliamentary Sovereignty

The UK joined the European Community on 1 January 1973 under the terms of the EU Treaty of Accession 1972. The European Communities Act 1972 (ECA 1972) incorporated the EU treaties into UK law and gave effect to the implications of membership of the European Community upon Parliamentary Sovereignty. Unlike other international law that had not been expressly incorporated into UK law by an Act of Parliament, the effect of the ECA 1972 was to give precedence to EU law above UK law in areas of EU competence.

In NV Algemene Transport- en Expeditie Onderneming Van Gend en Loos v Nederlandse Administratie der Belastingen (1963) Case 26/62 and Flaminio Costa v ENEL (1964) Case 6/64, the Court of Justice of the European Union (CJEU, formerly the European Court of Justice) held that Member States had limited their sovereign rights. The legal system created by the treaties formed an integral and binding part of the legal systems of Member States, involving a transfer of rights and obligations. Any subsequent legislation adopted by a Member State which was incompatible with EU law could not prevail.

In Blackburn v Attorney General [1971] 2 All ER 1380, the claimant argued that by agreeing to UK accession to the Treaty of Rome, the government would surrender part of the UK's Parliamentary Sovereignty and be in breach of the law. In the Court of Appeal, Lord Denning held that although in theory Parliament cannot bind its successors and cannot declare an Act of Parliament irreversible, legal theory must sometimes give way to practical politics. The claim failed. The treaty would not by itself change domestic law.

Sections 2 and 3 of the ECA 1972 gave effect to those Community rights, obligations and remedies which did not require further enactment and governed the determination of questions of Community law. In HP Bulmer Ltd & Anor v J. Bollinger SA & Ors [1974] EWCA Civ 14, the Court of Appeal refused to refer a case to the European Court of Justice on a matter of EC law on the grounds that it was not necessary to do so at that stage. While the ECA 1972 remained in force, EU law was supreme in areas of EU competence; ultimately, sovereignty still lay with Parliament, since the ECA 1972 could be repealed by Parliament. Lord Denning MR confirmed this in Macarthys Ltd v Smith [1979] 3 All ER 325 (CA). The ECJ gave its ruling on equal pay in Case 129/79 in 1980.

One consequence of the supremacy of EU law was the adoption of the purposive approach to statutory interpretation. In Pickstone v Freemans plc [1989] AC 66, the House of Lords took a purposive approach to section 1(2)(c) Equal Pay Act 1970, to give an interpretation of the provision that accorded with Article 119 EC Treaty.

In Litster v Forth Dry Dock & Engineering Co Ltd [1988] UKHL 10, [1990] 1 AC 546, the House of Lords determined that regulations enacted in 1981 were expressly enacted to give effect to Council Directive 77/187/EEC, which safeguarded employees' rights on the transfer of a business. UK courts were under a duty to adopt a purposive approach to the interpretation of regulations in a manner which would accord with the Directive as interpreted by the European Court. The protection extended to employees dismissed immediately before the transfer because of it.

In the litigation that led to R v Secretary of State for Transport, ex parte Factortame (Case C-213/89) [1990] 2 Lloyd's Rep 351 (Factortame No. 1), the High Court referred the substantive questions about the compatibility of the Merchant Shipping Act 1988 (MSA) with the EC Treaty to the ECJ in a separate reference (Case C-221/89). The High Court granted an interim order disapplying the relevant provisions of the MSA. The Court of Appeal reversed this decision, holding that the English courts had no jurisdiction to disapply an Act of Parliament. The presumption was that the Act was compatible with EC law until declared incompatible.

The House of Lords referred the interim relief question (Case C-213/89) to the ECJ, requesting clarification as to whether a national court was under an obligation to provide an effective interlocutory remedy to protect a party from irreparable damage. The ECJ found that a rule of national law which acts as the sole obstacle to interim relief in a case concerning EC law must be set aside. The House of Lords then granted interim relief. In Case C-221/89 the ECJ subsequently found that the nationality, residence and domicile requirements for fishing vessel registration in the Merchant Shipping Act 1988 contravened EC law.

In Thoburn v Sunderland City Council [2002] EWHC 195 (Admin); [2003] QB 151, a number of retailers appealed convictions for breach of regulations which required food to be sold in metric weights. They claimed that the Weights and Measures Act 1985 and regulations made under it impliedly repealed the ECA 1972 to the relevant extent. Laws LJ held that the ECA 1972 was a 'constitutional statute' and at common law was not subject to ordinary implied repeal. Its repeal required an actual intention shown by express words or words so specific that the inference was irresistible. On accession to the EC Treaty, the UK had subjected itself to a new and unique legal order in which, by virtue of the ECA 1972, directly effective rights and obligations created by EU law were incorporated into domestic law and ranked supreme over inconsistent domestic legislation.

Section 18 European Union Act 2011 confirmed that directly applicable or directly effective EU law only took effect in the UK by virtue of the ECA 1972 or another Act requiring it to be recognised. The section was enacted to allay concerns that the doctrine of Parliamentary sovereignty might in the future be eroded by the decisions of courts. It did not alter the existing relationship between EU and UK law.

G. Brexit and the Restoration of Parliamentary Sovereignty

In the 2016 EU referendum, the UK electorate voted to leave the European Union by 52% to 48%. In the landmark case of R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5, the Supreme Court held that the government could not use the royal prerogative to trigger Article 50 of the Treaty on European Union (the formal notification of intention to withdraw). An Act of Parliament was required because withdrawal would change domestic law by removing rights that Parliament had created through the ECA 1972. This decision reaffirmed that Parliamentary sovereignty required Parliament's authorisation for fundamental constitutional changes.

Parliament subsequently enacted the European Union (Notification of Withdrawal) Act 2017, authorising the Prime Minister to notify the European Council of the UK's intention to withdraw.

The European Union (Withdrawal) Act 2018 (EUWA 2018) repealed the ECA 1972 with effect from 31 January 2020 (known as 'exit day'). Its effect was saved with modifications for the transition period. At 11 pm UK time on 31 December 2020, the 2018 Act preserved specified categories of EU-derived law as 'retained EU law' to ensure legal continuity. Section 5(1), as then in force, excluded EU supremacy for domestic legislation passed or made after that point. Section 5(2) preserved it where relevant to earlier legislation.

The Retained EU Law (Revocation and Reform) Act 2023 (REUL Act) abolished the general principle of EU supremacy in domestic law at the end of 2023. The remaining body of retained EU law became 'assimilated law'. Domestic enactments generally take priority over assimilated direct legislation, subject to statutory exceptions. The changes do not generally govern events occurring before the end of 2023.

Parliament expressly recognised its continuing sovereignty in s.38 of the European Union (Withdrawal Agreement) Act 2020. Under s.7A of the EUWA 2018, domestic legislation takes effect subject to rights and obligations under the Withdrawal Agreement which are to have effect without further enactment. In Re Allister [2023] UKSC 5 this modified the effect of Article VI of the Acts of Union in Northern Ireland. In Re Dillon [2026] UKSC 15, the Supreme Court found no breach of Article 2(1) of the Windsor Framework on the facts, so the question of disapplication did not arise. The UK–EU Trade and Cooperation Agreement (TCA) concluded in December 2020 also contains binding international obligations and is implemented domestically, in part, by s.29 of the European Union (Future Relationship) Act 2020.

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