Documents to download

What questions have been raised?

Since the EU referendum in June 2016, several questions have been raised in national courts in the UK and other EU Member States and before the Court of Justice of the EU (CJEU) that concern Brexit – some directly, some indirectly. Several have been about the Brexit process in the UK and under Article 50 of the Treaty on European Union (TEU); others concern, for example, the implications of Brexit for citizens’ rights, UK extradition requests and matters of EU law that could be significant for future EU-UK relations.

Questions about the Brexit process

  • the exclusion of long-term expatriates from voting in the EU referendum
  • electoral irregularities in the referendum campaign
  • the UK Parliament’s role in triggering Article 50 TEU (the Miller case)
  • the legality of the European Commission’s ban on Brexit discussions with the UK before the triggering of Article 50 TEU
  • the legality of the Brexit negotiations
  • the revocability of Article 50 TEU
  • agreeing to extend Article 50 was illegal
  • the prorogation of Parliament and a no-deal Brexit

Other matters

  • EU citizenship rights
  • the extradition of convicted criminals to the UK under European Arrest Warrants
  • EU trademark protection
  • dispute settlement mechanisms and the autonomy of EU law

Funding of campaigns

Several of the challenges have been crowdfunded, mostly coordinated by the ‘Good Law Project’ and led by Jolyon Maugham QC. 


For the most part, the citizens’ challenges have not progressed to or been successful at the CJEU, but there have nonetheless been some significant developments in the UK and EU courts.        


  • The Miller case resulted in the UK Parliament enacting legislation to authorise the triggering of Article 50, rather than the Government doing so under prerogative powers.


  • In Miller it was taken as given that the notification made under Article 50 TEU was irrevocable, and the point was not argued despite its potential significance. But the Inner House (the appellate chamber of the Scottish Court of Session) judgment in Wightman and others, 21 September 2018, means that there will be a ruling from the CJEU, scheduled for 10 December, on whether the Article 50 notice can be unilaterally revoked by the UK as a matter of EU law. The Advocate General’s Opinion on 4 December 2018 was that unilateral revocation was permissible. The CJEU ruled on 10 December 2018 that that unilateral revocation of Article 50 was a sovereign right for any Member State to pursue without any conditions attached, beyond the decision to revoke notification needing to follow a ‘democratic process’ that satisfied national constitutional requirements and that the revocation would have to be made before a concluded withdrawal agreement had entered into force or (if there was no agreement) before the Article 50 negotiating period had expired (whether extended by unanimous European Council agreement or not).

         English Democrats

  • Relying heavily on Miller, the English Democrats have challenged the Prime Minister’s legal authority to ask for and agree to an extension to Article 50 using the Royal Prerogative, thereby postponing exit day.


  • In Shindler the General Court dismissed the action as “inadmissible”. The applicants appealed but the CJEU Fourth Chamber dismissed the appeal in April 2019.


  • In Wilson and others, the High Court emphasised that the courts’ job was not to rule on highly political matters (irregularities in the ‘leave’ campaign) but on questions of law.

         European Arrest Warrants

  • The CJEU judgment in RO,18 September 2018, concerns the lawful execution by Member States under EU law of European Arrest Warrants (EAWs) issued by the UK. The CJEU ruled that, all other requirements of the EAW Framework Decision being satisfied, the UK EAWs should continue to be executed in the lead-up to Brexit. The CJEU did not speculate about a transition/implementation period.

         Dispute settlement

  • The CJEU ruling in Achmea (dispute settlement) suggests that after Brexit the UK will not be able to avoid the impact of EU law and the CJEU.

         Proroguing Parliament

  • Appeals were brought in two cases where courts said the Prime Minister may prorogue Parliament, even though the timing of the prorogation might affect attempts in Parliament to avoid or prevent a no-deal Brexit (Gina Miller, Joanna Cherry and others). At appeal the Supreme Court ruled on 24 September that the prorogation of Parliament in early September was “unlawful”.

More to come?

CJEU President, Professor Koen Lenaerts, believes that many more Brexit cases will come before the CJEU before and after the UK leaves the EU.

Documents to download

Related posts