The Court of Justice of the European Union is the ultimate arbiter on certain Articles of the Protocol, and has an indirect role in interpreting EU laws as part of the agreed arbitration process. 

During an interview on BBC Radio Ulster’s The Nolan Show on 11 October 2021 (starts 23:43), the TUV leader, Jim Allister MLA, claimed that the European Court of Justice — as part of the Court of Justice of the European Union (CJEU) — is the supreme court regarding any challenge to the Northern Ireland Protocol:

“You know, in any international trade deal, the mechanism for arbitration is independent arbitration. In this protocol, it’s so one-sided that the arbitrator is the EU themselves… [The Court of Justice of the European Union is] their supreme court. Northern Ireland has a supreme court. It sits in London, but not under the protocol. Under the protocol, our supreme court on all protocol issues sits in Luxembourg.”

In a previous fact check, FactCheckNI explained how EU law applies in Northern Ireland under the Protocol. We concluded that the legal implementation of the Protocol had already been provided for in UK law, and that any necessary legislation can be passed in the Northern Ireland Assembly or in the UK Parliament at Westminster, according to respective legal competence and political will.

What does “supreme court” mean here?

This fact check considers the enforcement and dispute resolution mechanisms set out in the UK-EU Withdrawal Agreement and the Protocol, in relation to the implementation of the Protocol.

While the European Court of Justice (ECJ) is often singled out in discussion and debate, it is just one of three courts that make up the Court of Justice of the European Union (CJEU). The other two courts are the General Court, and the European Civil Service Tribunal. This fact check considers the CJEU, as all three component courts retain jurisdiction in respect to specified Articles of the Protocol.

Mechanisms for the enforcement of the Protocol

The UK-EU Withdrawal Agreement, including the Protocol, established two mechanisms for ensuring that the Protocol is enforced and/or that disputes concerning its implementation can be resolved:

  1. the Court of Justice of the European Union has jurisdiction for any disputes arising under Article 12(2), Article 5 and Articles 7 to 10 of the Protocol; and
  2. an arbitration panel to handle any disputes arising under those Articles not directly covered by the CJEU continued powers (i.e., Articles 1 to 4, Article 6, and Articles 11 to 19).

Let’s consider the nature of these two enforcement mechanisms in greater detail.

CJEU jurisdiction

Under Article 12(4) of the Protocol, the Court of Justice of the European Union retains jurisdiction in the United Kingdom for the purposes of ensuring certain aspects of the Protocol are enforced.

This means that the EU’s highest court — the CJEU — has “full jurisdiction” in relation to the operation of EU law that applies to Northern Ireland in certain areas. The areas covered are:

  • customs and the movement of goods (Article 5)
  • the monthly exchange of information on customs matters (Article 12(2), second subparagraph)
  • technical regulations (Article 7)
  • VAT and excise (Article 8)
  • the single electricity market (Article 9), and
  • state aid (Article 10)

Furthermore, Article 12(5) says that the application of EU law in Northern Ireland that flows from these Articles must produce “the same legal effects as those they produce within the [European] Union and its Member States”. In legal terms, this means that all the “normal” features of EU law apply here, including, for example: primacy of EU law over domestic law, the direct effect of EU law without further enactment, and state liability if the UK fails to enact relevant provisions.


Under Article 13(1) of the Protocol, the section of the UK-EU Withdrawal Agreement that deals with the “dispute resolution” mechanism (Part Six) applies “without prejudice” to the Protocol. So the arbitration process created for resolving disputes that generally arise under the Withdrawal Agreement also applies to the implementation of the Protocol and, most specifically, to those aspects (below) not explicitly covered by CJEU jurisdiction.

  • Premises and Purpose (Preamble)
  • Objectives (Article 1)
  • Individual Rights (Article 2)
  • Common Travel Area (Article 3)
  • UK Customs Territory (Article 4)
  • Protection of the UK Internal Market (Article 6)
  • Other Areas of North-South Cooperation (Article 11)
  • Implementation, Application, Supervision and Enforcement (Article 12 (excluding (2))
  • Common Provisions (Article 13)
  • Specialised Committee (Article 14)
  • Joint Consultative Working Group (Article 15)
  • Safeguards (Article 16)
  • Protection of Financial Interests (Article 17)
  • Provision for a democratic consent vote in Northern Ireland (Article 18), and the
  • Annexes (Article 19)

The CJEU does not have a direct role in this arbitration process. However, if there is a dispute between the UK and EU concerning the interpretation of an instrument of EU law, then the arbitration panel would “request the Court of Justice of the European Union to give a ruling on the question” (Article 174(1)). Therefore, the CJEU could still have an indirect role in determining the outcome of a dispute concerning the implementation of the Protocol, even in matters not explicitly covered by its continued jurisdiction.

Are the mechanisms for the enforcement of the Protocol unconventional? 

It is fair to say that the enforcement mechanism(s) — CJEU jurisdiction and arbitration — created to oversee the implementation of the Protocol are unconventional. Jim Allister pointed out that international trade agreements normally define an independent arbitration process to settle disputes. Though it should be noted that the Withdrawal Agreement is not a trade agreement; it is an agreement to deal with the implications of the UK’s withdrawal from EU Treaties it previously signed up to. And the Protocol is an appendix to this Withdrawal (not trade) Agreement, designed to address the “unique circumstances” on the island of Ireland created by the UK’s decision to withdraw from the EU.

Given the bespoke nature of both the Withdrawal Agreement and the Protocol, it may be unsurprising that the mechanisms for its enforcement and for the resolution of disputes should they arise, are sui generis (unique) in international law terms.

Is the CJEU the sole arbiter on all Protocol issues?

No. But it is complicated. The CJEU is the ultimate arbiter on matters related to the implementation of certain Articles of the Protocol (those that address customs, movement of goods, customs information exchange, technical regulations, VAT and excise, and state aid). For areas not explicitly covered, the CJEU retains a role within the agreed process of arbitration, interpreting EU laws as part of the process of settling disputes between the UK and EU over the implementation of the Protocol.

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