• Several unionist politicians brought a challenge against the legality of the NI Protocol
  • That case was ultimately dismissed by the Supreme Court last month
  • The appellants put three separate arguments to the court, saying the Protocol was incompatible with provisions in the Acts of Union and the Northern Ireland Act
  • They claimed that the NI Protocol clashed with citizens’ rights regarding trade and the negotiation of treaties, that its implementation breached the principle of consent, and that the voting system whereby Stormont could in future endorse or reject the Protocol was unlawful because it sidestepped petitions of concern
  • The Supreme Court rejected the principle-of-consent argument wholesale
  • For the other arguments, its rulings against the appellants relied on the sovereignty of Parliament, and the fact that the legislation enacting the Protocol had the power to modify earlier laws – including both the Acts of Union and the Northern Ireland Act
  • FactCheckNI looks at what the court actually decided at the end of this long-running case

On 8 February, the Supreme Court handed down judgment in a case challenging the legality of the Northern Ireland Protocol.

The court unanimously rejected the arguments of several unionist politicians (and others), and found that the Protocol was lawful in all respects.

This article looks in some detail at what the Supreme Court was asked to consider, and what it actually said about the arguments it ultimately dismissed.


In February 2021, judicial review proceedings challenging the lawfulness of the Northern Ireland Protocol were brought against the Prime Minister, the Secretary of State for Northern Ireland, and the Chancellor of the Duchy by a member of the public, Clifford Peeples.

A month later, similar proceedings were brought by a cross-party group of unionists including TUV leader Jim Allister, former First Minister Arlene Foster, former Tory and Brexit Party MEP Ben Habib, Baroness Hoey of Lylehill, former UUP Leader and First Minister Lord Trimble and former UUP Leader and standing MLA Steve Aiken.

Both sets of proceedings were heard together by Mr Justice Colton in the Northern Ireland High Court, and later dismissed in a ruling handed down on 30 June 2021. Following appeal, both proceedings were again heard together this time in the Court of Appeal in Northern Ireland and dismissed in a ruling handed down on 14 March 2022.

The appellants were given permission for a further appeal to the Supreme Court on three of the five arguments they had put forward.


This Supreme Court heard this case on 30 November and 1 December last year. Over those two days, the legality of the Protocol was challenged on three grounds:

  1. Incompatibility with Article VI of the Acts of Union 1900
  2. Incompatibility with section 1(1) of the Northern Ireland Act 1998
  3. Incompatibility with section 42 of the Northern Ireland Act 1998

Acts of Union

The Acts of Union 1800 established the Union of Great Britain and Ireland.

The appellants focused on what they said were “two distinct limbs” of Article VI of the Acts – one concerning trade and another concerning treaties.

Article VI states that subjects of the Union shall:

“…be entitled to the same privileges and be on the same footing, as to encouragements and bounties [the trade limb] … and that in all treaties made by [His] Majesty, his heirs, and successors, with any foreign power, [His Majesty’s subjects of Ireland shall have the same privileges and be on the same footing as [His] Majesty’s subjects of Great Britain [the treaty limb]

On trade, the appellants argued that, because goods entering NI from GB are required to follow EU rules rather than UK rules, the Protocol has undermined the “same footing” guarantee.

Regarding treaties, they said the Protocol restricts the UK Government’s prerogative powers to negotiate treaties on the “same footing” for all subjects.

Dismissing both limbs of the appellants’ first argument, the Supreme Court drew upon “the most fundamental rule of UK constitutional law” – namely that “the Crown in Parliament is sovereign, and that legislation enacted by Parliament is supreme.”

Addressing the trade limb, the court said that, while the domestic law that gives the Protocol legal force in the UK provides a “modification” of Article VI, this “does not amount to a repeal of that article.”

Section 7A(3) of the European Union (Withdrawal) Act 2018 states that “[every] enactment [in UK law] is to be read and has effect subject to subsection (2)” which provides for “all such … obligations and restrictions from time to time created or arising by or under withdrawal agreement [including the Protocol]” are to be recognised and available in domestic law and to be enforced, allowed and followed accordingly. 

The court said this language provides a “clear answer” to the appellants’ question by saying that any other UK law enactments are to be read subject to the provisions of the 2018 Act and, because it was approved by the UK parliament long after Article VI of the 1800 Acts, the later Act takes precedence. 

Addressing the treaty limb argument, the Supreme Court said that, because Parliament approved the terms of the agreement the government negotiated with the EU when it passed the European Union (Withdrawal Agreement) Act 2020 and assented to their implementation in domestic law, the UK-EU treaty containing the Protocol was lawfully made.

Section 1(1) of the Northern Ireland Act

The first section of the Northern Ireland Act 1998 implemented some of the commitments made in the Good Friday Agreement, often referred to as the principle of consent.

Section 1(1) of the Act says “Northern Ireland in its entirety remains part of the United Kingdom” and this “shall not cease to be so without the consent of a majority of the people of Northern Ireland” voting in a dedicated poll.

Section 1(2) states that if “Northern Ireland should cease to be part of the United Kingdom and form part of a united Ireland” then the UK government will support this with legislation.

The appellants argued that section 1(1) not only regulates the specific type of constitutional change noted in section 1(2) but also has a wider meaning – and it protects against any diminution of Northern Ireland’s status within the UK, except when this has been approved at the ballot box.

They said the Protocol amounted to a diminution and that no majority consent of people in NI had been sought or received. Therefore, they argued, the legislation behind the Protocol was unlawfully made.

The Supreme Court relied on an earlier ruling from 2017 in a landmark Brexit case brought initially by Gina Miller. One of the appellants in Miller No. 1, Raymond McCord, had argued that Brexit itself breached the principle of consent. This line of argument was rejected. In Miller No. 1, it was the Supreme Court’s unanimous view that section 1(1):

“…gave the people of Northern Ireland the right to determine whether to remain part of the United Kingdom or to become part of a united Ireland. It neither regulated any other change in the constitutional status of Northern Ireland nor required the consent of a majority of the people of Northern Ireland to the withdrawal of the United Kingdom from the European Union”

Affirming this earlier judgement, the court dismissed the appellants’ second ground of appeal.

Section 42 of the Northern Ireland Act

The third ground of appeal focused on a specific aspect of the Protocol: the democratic consent mechanism, contained in Article 18 of the text.

That article gives the Northern Ireland Assembly the opportunity to vote in favour or against the continued application of Articles 5 to 10 of the Protocol (which relate primarily to cross-border trade in goods and, thus, the avoidance of a physical hard border on the island of Ireland) in 2024 and at regular intervals thereafter.

According to Article 18 of the Protocol, if a simple majority of MLAs vote in favour of the continuation of Articles 5 to 10, then another vote will be held four years later. If a cross-community majority vote in favour, the next vote will be eight years later. This means cross-community consent is not required for continuation, although it does have an effect on the frequency of votes.

The appellants said this situation is unlawful because it required the setting aside of the mechanism for petitions of concern which ordinarily enables decisions in the NI Assembly to be made only with cross-community consent, if enough MLAs deem this necessary.

They based this argument on the fact that the 2018 EU Withdrawal Act requires all measures made under its purview to be compatible with the 1998 Northern Ireland Act.

The UK Government, as respondents in the Supreme Court case, said the continued application of Articles 5 to 10 of the Protocol is a matter of international relations and, therefore, an explicitly “excepted” matter – meaning it is not the responsibility of Stormont – so strict adherence to the petition-of-concern mechanism is unnecessary.

The appellants countered the government by arguing that section 42 of the 1998 Act uses clear but broad language that the petition-of-concern mechanism is applicable to “a matter which is voted on by the Assembly”, therefore the petition-of-concern process should be applicable to all Stormont votes regardless of whether they concern devolved matters.

The Supreme Court acknowledged “the potential force of the appellants’ argument that section 42” of the 1998 Act applies to any Assembly vote, regardless of whether or not it is on a devolved matter.

However, the court decided it wasn’t necessary to determine whether or not this argument was correct because the supposed incompatibility – between the system for voting for or against continuation of Articles 5 to 10 of the Protocol and section 42 of the 1998 Act – did not arise.

They ruled this was because the 1998 Act had already been changed by section 7A of the 2018 Act prior to the creation of the regulations for the democratic consent mechanism.