The Court of Justice of the EU (CJEU) interprets EU law. Its purpose is to ensure the uniform application of EU law across all Member States. The UK is no longer a member of the EU, but the CJEU will continue to play a role in UK law.

This Insight explains what role the CJEU will play in the UK during the transition period and beyond.

What is the jurisdiction of the CJEU during the transition period?

During the transition period nearly all EU rules will continue to apply to the UK. The jurisdiction of the CJEU in the UK will also mostly continue as it did when the UK was a Member State. This means that during the transition period, the CJEU can rule on the following types of actions involving the UK:

  • Infringement proceedings under Article 258 of the Treaty on the Functioning of the EU (TFEU). If the Commission believes that the UK has failed to comply with any EU law obligations, it can bring a case before the CJEU against the UK. This is stated in Article 158 of the WA.
  • Annulment actions under Article 263 TFEU. If EU bodies take decisions involving the UK before the end of the transition period, the UK can challenge the legality of these decisions before the CJEU.
  • Preliminary references submitted by UK courts under Article 267 TFEU. If UK courts have questions about the interpretation of EU law when deciding a domestic dispute, they can (or in the case of the Supreme Court, must) ask the CJEU for an interpretation of that EU law concept. This is in Article 86(2) of the WA.

What is the jurisdiction of the CJEU after the transition period?

The transition period and the application of EU law in the UK ends on 1 January 2021 (unless extended). However, under the WA the CJEU’s jurisdiction continues beyond the transition period in some areas.

First, its jurisdiction over concepts of EU law that arise over the interpretation and application of the WA lasts as long as aspects of the WA remain in operation. In the case of Part 2 of the WA on citizens’ rights, this is as long as EU citizens and UK nationals covered by Part 2 remain alive. For an explanation of Part 2 of the WA see the Library’s research briefing The October 2019 EU-UK Withdrawal Agreement. In the case of the Protocol on Ireland/Northern Ireland, the CJEU’s jurisdiction could be indefinite.

Article 86(1) of the WA makes it clear that any cases pending before the CJEU at the end of the transition period will fall within the CJEU’s jurisdiction until they are finalised. This includes decisions on appeals.

Article 87 of the WA adds to this more specifically. It states that the European Commission has four years from the end of the transition period to bring infringement proceedings against the UK for breaches of EU law that took place during the transition period.

Any judgment handed down by the CJEU that is covered by these provisions will remain binding on the UK. As such, it is possible that a proceeding commenced by the European Commission in 2024 about a UK action (or failure to act) in 2020 will be decided by the CJEU in 2025, and will be binding on the UK.

The CJEU also gains one further form of jurisdiction under the WA after the transition period. If the UK and the EU disagree about the interpretation and application of the WA, and they cannot resolve this dispute through consultations, an arbitration panel can be established to resolve the dispute in a binding manner under Article 170 of the WA.

If this panel has to consider the meaning of a concept of EU law, under Article 174 WA it is obliged to ask the CJEU to offer a binding interpretation of that concept of EU law. The panel must then apply that interpretation to the dispute before it. The CJEU will not be involved in disputes that do not involve concepts of EU law, and will not decide on the dispute between the UK and the EU itself. 

Finally, there are two aspects of CJEU jurisdiction after transition that are treated distinctly in the WA. Firstly, to ensure that Part 2 is interpreted in the same way in the UK and in the EU, UK courts retain the power to send preliminary references to the CJEU about the meaning of any aspect of Part 2 of the WA for a period of eight years after the end of the transition period. Questions about EU citizens’ rights in the UK can thus continue to be submitted to the CJEU until at least the end of 2028.

The second aspect relates to Articles 136 and 138 of the WA, covering aspects of the financial settlement agreed with the EU. The UK, under the WA, will continue to make payments to the EU after 31 December 2020. The infringement proceedings under Article 258 TFEU and preliminary references under Article 267 TFEU will continue to apply to the UK. This will enable UK courts to ask the CJEU questions about aspects of the financial settlement (as set out in Articles 136 and 138 WA). It will also allow the European Commission to enforce the financial settlement before the CJEU.

What will the CJEU’s jurisdiction be in the ‘future relationship’?

Under the WA, the CJEU will no longer have general jurisdiction over the UK in relation to any acts that take place on or after 1 January 2021. Whether it will have any role to play in terms of oversight of any future relationship agreements between the UK and the EU will depend on what is negotiated.

The Political Declaration agreed by the UK and the EU, only makes clear that insofar as the ‘future relationship’ contains concepts of EU law, disputes about those concepts will have to be referred to the CJEU. This must be in a process similar to that set up by Article 174 of the WA, in which the CJEU can offer a binding interpretation of EU law.


This Insight was updated on 10.02.20. It previously stated that the UK would lose its broader Article 263 TFEU powers during the transition (apart from in relation to state aid or competition law). It has been corrected to state that the UK retains these powers during the transition period. It also stated that the dispute mechanisms, involving the arbitration panel and related CJEU role under Articles 170 and 174 of the WA, would commence at the beginning of the transition period. It has been corrected to state that these mechanisms do not commence until after the transition period.    

Further Reading

The UK’s EU Withdrawal AgreementHouse of Commons Library

The October 2019 EU UK Withdrawal AgreementHouse of Commons Library

Analysis 2 of the Revised Brexit Withdrawal Agreement: Transition PeriodEU law analysis blog.


About the author: Sylvia de Mars is a senior researcher in international affairs and defence at the House of Commons Library, specialising in EU and international law. 

Photo: G. Fessy, The Main Courtroom, © Court of Justice of the European Union