Brexit Institute News

The Supreme Court judgment in Re Allister et al—Constitutional statutes, quo vadis?

John Bell (Queen Mary University of London)


Three years after the end of the transition period, it is worth reflecting on how Brexit has laid  bare the fundamentals of UK constitutional law. The Supreme Court judgment in Miller 1 [2017] UKSC 5 now sits in the pantheon of ‘must read’ constitutional case law for its exposition of Parliamentary supremacy, nullifying a Prerogative Order in Council as if it were a Proclamation of James I.

Perhaps not quite in the pantheon alongside Miller, the unanimous Supreme Court judgment in Re Allister et al.  [2023] UKSC 5 is a simple and useful illustration of the supremacy of the Crown in Parliament.

That said, I argue that the judgment has implications for the evolving common law concept of constitutional statutes formulated by Laws LJ in Thoburn v Sunderland City Council [2002] EWHC 195 (Admin). If one Act of Union can be overridden, what does this mean for the Acts of Union 1707? The latter, of course, is no stranger to the Supreme Court in recent months and raises issues of Scots law.

In this article, I will address the (relatively) straightforward application of Parliamentary supremacy in Allister et al and examine the implications of the judgment for the concept of constitutional statutes.

  1. A relatively straightforward application of Parliamentary supremacy

The appellants contended the existence of a conflict between the Union with Ireland Act 1800 and Act of Union (Ireland) 1800 (Acts of Union 1800) and the Northern Ireland Protocol to the Withdrawal Agreement, given effect in UK law by the European Union (Withdrawal) Act 2018 (EU(W)A 2018).

The relevant ground of appeal relied on Article VI of the Acts of Union 1800, which provides that (a) His Majesty’s subjects of Great Britain and Ireland shall be on the ‘same footing’ in terms of trade, and (b) the Prerogative cannot be exercised to enter into a treaty which does not provide for His Majesty’s subjects in Great Britain and Ireland to be on the ‘same footing’ in terms of trade. The Supreme Court termed (a) the ‘trade limb’ and (b) the ‘treaty limb.’

On both limbs, the Supreme Court dismissed the relevant grounds of appeal on the basis that EU(W)A 2018, s 7A provides for the Withdrawal Agreement to be given direct effect in UK law, with the disapplication of inconsistent or incompatible legislation.

This is a straightforward application of the Diceyan orthodoxy. As pithily expounded by the Supreme Court at paragraph 66 its judgment:

‘The most fundamental rule of UK constitutional law is that Parliament, or more precisely the Crown in Parliament, is sovereign and that legislation enacted by Parliament is supreme.’

As the ratio of the judgment, that is the end of the story. The express provisions of one Act of Parliament trumped an earlier Act of Parliament.

An interesting nuance regarding the ‘treaty limb’ is that the appellants contended it was the exercise of the Prerogative power to enter into the Withdrawal Agreement which was unlawful. The Court of Appeal had held the issue non-justiciable in a predictable application of GCHQ [1985] 1 AC 374.

By contrast, the Supreme Court approached the issue through the prism of Parliamentary supremacy, following the dicta in GCHQ  that Parliament can impose restrictions on the Prerogative to enter into treaties as consistent with Parliamentary supremacy.

Perhaps understandably, the Supreme Court did not elaborate on this point. Yet if, as the Supreme Court opined, Parliament can place legislative restrictions on the Prerogative to enter into treaties inconsistent with Parliamentary supremacy, what was the intention of the 1800 Parliament of Great Britain in drafting the ‘treaty limb’ of Article VI?

The Northern Ireland Court of Appeal judgment in Allister et al [2022] NICA 15 at para 110 is revealing: ‘The more general words of the Act of Union 1800 written 200 plus years ago in an entirely different economic and political era could not override the clear specific will of Parliament, as expressed through the Withdrawal Agreement and Protocol, in the context of the modern constitutional arrangements for Northern Ireland (my emphasis).’

Although not repeating these words, the Supreme Court held that a ‘clear answer’ has been provided by the EU(W)A 2018.

What remains unclear is the status of constitutional statutes.

  1. Constitutional statutes—quo vadis?

 Whilst the substance of the judgment is a relatively straightforward application of the Diceyan orthodoxy, I contend that it has implications for the concept of constitutional statutes in UK law.

As formulated by the High Court in Thoburn, Laws LJ distinguished between ‘ordinary statutes’ which could be impliedly repealed, and ‘constitutional statutes’ which could only be expressly repealed. Laws LJ listed the following as constitutional statutes: Magna Carta 1297, the Bill of Rights 1689 [1688], the Union with Scotland Act 1706, the Reform Acts, the Human Rights Act 1998, the Scotland Act 1998 and the Government of Wales Act 1998.

Laws LJ opined that the latter could only be repealed (or a fundamental right abrogated) by ‘express words in the later statute, or by words so specific that the inference of an actual determination to effect the result contended for was irresistible.’ The Court of Appeal (at para 110) paraphrased Laws LJ in Thoburn  to give EU(W)A 2018 ‘interpretative supremacy’ over the ‘open-textured’ Article VI of the Acts of Union 1800.

The Supreme Court in Allister et al did not examine in depth the wider context of constitutional statutes as a common law principle. This lack of engagement of the Supreme Court with Thoburn raises the possibility that the concept of constitutional statutes is no more.

Following the logic of the Supreme Court judgment, none of the Acts of Parliament described by Laws LJ in Thoburn would have any special status.

This is not a theoretical matter. The Union with Scotland Act 1706 and Union with England Act 1707 (Acts of Union 1707), themselves ‘written 200 plus years ago in an entirely different economic and political era’ have been no stranger to the Supreme Court in recent times. (See: REFERENCE by the Lord Advocate of devolution issues under paragraph 34 of Schedule 6 to the Scotland Act 1998 [2022] UKSC 31.)

Of course, English law is not the only jurisdiction in the UK. In the Scots law case of MacCormick v Lord Advocate 1953 SC 396, Lord President Cooper opined (at 411) that the ‘distinctively English principle’ of the ‘unlimited sovereignty of Parliament’, […] had ‘no counterpart in Scottish constitutional law.’ Indeed, a body of Scots jurists argue that the Acts of Union 1707 constitute ‘fundamental law.’ For which, see: Stair Memorial Encyclopaedia, Constitutional Law, 2. Fundamental Law, 62. The Union as fundamental law: general.

The petitioners in MacCormick argued that the Royal Proclamation pursuant to the Royal Titles Act 1953 was in breach of the Acts of Union 1707 on the basis Queen Elizabeth II should have been styled Queen Elizabeth I in Scotland and that the Proclamation unlawfully inferred that Elizabeth I had been Queen of Great Britain. The Court of Session dismissed the petition on the basis that examination of the Proclamation was non-justiciable.

As a matter of Scots law at least, a simple affirmation of the Diceyan orthodoxy does not complete the picture.

English common law contains principles of construction which impliedly limit general words in a statute. As held in R v Secretary of State for the Home Department, ex parte Pierson [1998] AC 539, Parliament is presumed not have intended to change the common law unless it has clearly indicated such intention either expressly or by necessary implication. Whenever a statutory decision-making power is conferred, it is presumed that Parliament intended the decision to be made in accordance with natural justice.

In short, a statutory power in general terms cannot be taken to limit a subject’s legal rights unless the statute makes clear the intention of Parliament. Even following these common law principles of statutory interpretation,  Parliament could still expressly repeal statutes like the Human Rights Act 1998. This takes us back to square one.

If the Supreme Court judgment in Allister et al really is the end of Thoburn, I argue that statutes of a constitutional nature could at worst be impliedly repealed, or at best be expressly repealed, by dint of common law if fundamental rights are concerned.


Once again, Brexit affords us with the opportunity to examine the wiring of the UK’s unwritten constitution. Yet, for all its orthodoxy, this latest Supreme Court judgment leaves us with more questions than answers.

Most of the constitutional statutes set out by Laws LJ in Thoburn have been the subject of legislative action in recent times. The Scottish Referendum Bill Reference in the Supreme Court raises unavoidable Scots law questions about the Acts of Union 1707 and the Bill of Rights Bill re-writes the ECHR.

A simple answer might be that Allister et al is a straightforward application of the orthodoxy of Parliamentary supremacy. I argue that closer inspection of the development of common law principle might just leave us wanting more. It remains to be seen whether Thoburn deserves a place in the pantheon.

John Bell, LLM (Queen Mary University of London), is a former Schuman Trainee at the European Parliament and regular contributor on Brexit matters.

The views expressed in this blog reflect the position of the author and not necessarily that of the Brexit Institute Blog.

Image credit: succo under a Pixabay License.

WordPress PopUp Plugin