Litigating Brexit: a guide to the case law

Professor Steve Peers, University of Essex

The following (initially posted on 24 July 2020) is a guide to the litigation relating to the Brexit process. I’ll update it regularly as cases develop (last updated 15 May 2024, section 11.a; see complete list of updates at the end). For further reading, see this House of Commons Briefing Paper, which has additional details of cases and further links to judgments and commentary (although note this briefing paper is up to date to 1 November 2019).

1              Referendum franchise and conduct

Harry Shindler challenged the exclusion of UK citizens living abroad for more than 15 years from the voting franchise for the referendum. He lost in the High Court (28 April 2016) on the grounds that while the voting limit engaged EU law, it did not limit free movement rights; even if it did, those limits would be justified. He appealed to the Court of Appeal (20 May 2016), which ruled that the voting limit was outside the scope of EU law and in any event did not limit free movement rights. The Supreme Court refused leave to appeal (24 May 2016) on the grounds that if EU law did apply, there was no limit on free movement.

Note that the right to free elections in the first protocol to the European Convention on Human Rights does not apply to referendums, unless they are de facto general elections: see the summary of the case law (para 4). Nor does it generally require states to extend voting rights to their citizens who live abroad: see, for instance, the judgment of the European Court of Human Rights in Shindler v UK.

In Ball v Johnson, a private prosecution for misconduct in public office based on Boris Johnson’s comments during the referendum campaign, a district judge originally issued a summons on 29 May 2019. However, this was quashed by a judgment of the High Court on 3 July 2019 (see discussion here).

The issue of breaches of election spending law during the referendum was also the subject of several decisions of the Electoral Commission and litigation. On some of these cases, see section 4.2 of the House of Commons Briefing Paper.

2              Parliamentary approval of leaving the EU

In Miller I (24 Jan 2017), the Supreme Court, following the High Court (3 Nov 2016; see also the  contrary Northern Ireland High Court ruling in McCord and others, decided with Miller I by the Supreme Court), ruled that the decision to leave the EU could not purely be an act of the executive, but had to be approved by Parliament (see discussion here). Parliament duly passed the EU (Notification of Withdrawal) Act, which conferred upon the Prime Minister the power to notify the EU of the intention to leave.

3              Validity of notification to leave the EU

The Prime Minister’s decision to leave the EU pursuant to a power conferred by the Act was identified and upheld in a judgment of the High Court (Webster, 12 June 2018). The court ruled that the Prime Minister had satisfied the obligations imposed by the Miller I judgment. See discussion on the Monckton chambers blog here.

In Wilson, it was argued that the notification was unlawful because of breaches of election spending law by the Leave campaigns (see section 1 above). Permission to bring the case was refused by the High Court on 10 December 2018; permission to appeal was refused by the Court of Appeal on 4 March 2019. 

4              Withdrawal process

Mr Shindler sued to annul the EU Council decision giving the EU Commission a mandate to negotiate the withdrawal agreement with the UK. The EU General Court (Case T-458/17, 17 Sep 2018) ruled against him (see analysis here), on the grounds that the decision did not directly affect the position of the applicants, because Brexit was caused by the decision of the UK to leave, which was not subject to approval of the EU institutions (see discussion here). The Court of Justice (Case C-755/18 P, 19 March 2019) rejected his appeal.

A further Shindler case (Case T-541/19) argued that the date of the 2019 European Parliament election should have been delayed because of the Brexit process. This action was dismissed by the EU General Court on 29 January 2020. An appeal against this ruling to the CJEU was dismissed in October 2020 (Case C-158/20 P).

5              Status of the UK during the withdrawal process

The CJEU ruled in Case C-327/18 PPU RO (19 Sep 2018; a case concerning the European Arrest Warrant, discussed here) and Case C-661/17 MA (23 Jan 2019; a case concerning the Dublin asylum responsibility rules, discussed here) that during the process of negotiating to leave the EU, the UK retained all rights and obligations of EU law. See also the judgment in Case C-340/17 on the EU trade mark pending withdrawal. The High Court ruled in February 2021 against a challenge to the loss of voting rights by some EU citizens in the UK in the 2019 European Parliament election (the 3million and others). This judgment was not appealed. 

6              Revocation of notification to leave the EU

The CJEU ruled in Wightman (10 Dec 2018) that the UK could withdraw the notification to leave unilaterally, up until the point when the withdrawal agreement entered into force or (taking account of extensions) the UK left the EU by virtue of the notification period running out. (See discussion of the judgment here and here; and discussion of the AG opinion of 4 Dec 2018 here) This followed a lengthy process in the Scottish courts, which eventually sent questions on the matter to the CJEU (see discussion of the domestic process here).

7              Withdrawal from the EU: impact on Scotland, Northern Ireland and Wales

The Supreme Court ruled on 13 December 2018 on the division of powers between Westminster and the Scottish Parliament as regards the process of withdrawal from the EU (see discussion here). On 12 September 2019, the High Court of Northern Ireland ruled against a number of arguments raised by McCord and others as regards the conduct of Brexit negotiations. An appeal to the Northern Ireland Court of Appeal was unsuccessful on 27 September 2019. 

In April 2021 the High Court ruled that the Welsh government could not bring a judicial review against provisions of the Internal Market Act, which regulates the trade and regulatory relationship between Westminster and devolved bodies post-Brexit. In June 2021 the Court of Appeal overturned that judgment, ruling that the Welsh government's challenge can proceed, but in February 2022 that court ruled against the legal challenge (see discussion by George Peretz). 

8              Prorogation

While the controversial prorogation of the House of Commons in autumn 2019 did not directly concern the legal aspects of the Brexit process, politically it was linked to disputes concerning Brexit. The Supreme Court ruled on 24 September 2019 (Miller II/Cherry) that the prorogation was unlawful. For analysis see here; for comments on the earlier phases of this litigation, with links to judgments, see here, here and here.

9              Extension of EU membership

The first extension of the UK's EU membership (see discussion here) was unsuccessfully challenged on the grounds that it breached domestic law (the Tilbrook litigation: see the House of Commons Briefing Paper, section 2.3). The third extension of EU membership (see discussion here) was based on the so-called Benn Act (discussed here), which required the UK government to request this extension if certain conditions were met. Since the government seemed to suggest that it would not comply with its obligations under the Act, there was litigation to enforce its obligations, although ultimately the government complied (see summary of the litigation here). As noted above (s 4), the EU courts have dismissed cases by UK citizens in the EU who argued that the EU should have postponed the 2019 EP elections in light of the late extension of UK membership.

10           UK citizens retaining EU citizenship

Three batches of cases have been brought arguing in various ways that UK citizens retain EU citizenship after Brexit. Some of them have raised other issues, in particular challenging the validity of the withdrawal agreement on other grounds.

A first batch of cases was brought before Brexit Day. In Walker, it was argued that the EU legislation exempting UK visitors from short-term visas after Brexit (discussed here) was invalid, on the grounds that it infringed the status of UK citizens after Brexit. An interim measures claim was dismissed in the EU General Court (Case T-383/19 P, 23 Oct 2019), and on appeal by the Court of Justice (Case T-789/19 P, 7 Feb 2020). The main case was later dismissed by the EU General Court (16 June 2020; see Twitter thread). The courts have consistently ruled that the applicants lack standing, in that UK citizens as a group (even those in the EU) do not have sufficient ‘individual concern’ to challenge EU legislation.

In another Shindler case (Case T-627/19), it was argued that the Commission had a legal obligation to order Member States to establish a special status for resident UK citizens. An interim measures claim was dismissed in the EU General Court (29 Jan 2020). The main case was later dismissed in the EU General Court (14 July 2020) on the grounds that the Commission has no such powers (see extracts in English).

The second batch of cases was brought before the EU courts after Brexit Day. These comprise Case T-198/20 Shindler, Case T-231/20 Price and Case T-252/20 Silver. An interim measures request in the Price case was dismissed by the EU General Court for lack of standing (24 June 2020; for discussion see Twitter thread); the CJEU rejected the appeal in December 2020 (Case C-298/20 P). On 8 June 2021 the General Court rejected each of these cases (see orders in Price, Shindler and Silver) as inadmissible (see discussion in Twitter thread), because UK citizens lacked 'individual concern' to sue in the EU courts against the withdrawal agreement, and the decision concluding the withdrawal agreement is not a 'regulatory act'. In August 2021, these rulings were appealed to the CJEU (see respectively Price, Shindler and Silver). It should be noted that these cases, had they been successful, would not have "annulled Brexit" (see Twitter thread). The CJEU dismissed all these cases on 15 June 2023.  

A third batch of cases raises this issue in the national courts (where the Price interim measures ruling suggested that they should be brought). Litigation was brought in the Dutch courts in 2018 (see discussion here): the first instance court referred questions to the CJEU, but an appeal court halted the litigation and it did not progress further. In spring 2020, the French Conseil d’Etat did not need to decide a case concerning the (now irrelevant) national legislation adopted in the event of ‘no deal’ (meaning, in this context, 'no withdrawal agreement'). A further case had a hearing in the Cour de Cassation in France in September 2020. On October 1st 2020 that court ruled against the arguments and refused to send questions to the CJEU. This case has now been filed before the European Court of Human Rights.

However, in November 2020 a tribunal decided to send questions to the CJEU on the EU citizenship issues, including the validity of the withdrawal agreement (Case C-673/20 - see summary of the case). An Advocate-General's opinion in this case was released on 24 February 2022, rejecting the argument that UK nationals retained EU citizenship after Brexit (see analysis here). The judgment, on June 9 2022, also rejected the argument (see analysis here). In December 2020 a second national court decided to refer questions to the CJEU (Case C-32/21). This case was withdrawn in November 2022, following the earlier judgment in the first case. 

In November 2022, a third case, about the loss of the right to vote for European Parliament elections, was referred. (The previous cases concerned the loss of the right to vote in local elections). The CJEU rejected this argument in April 2024.

11         Withdrawal agreement

a) Northern Ireland protocol/Windsor Framework

Due to concerns about the UK's government's expressed intention to breach the withdrawal agreement, set out in the UK Internal Market bill tabled in September 2020 (see discussion here, here and here), the EU Commission raised the question of a possible legal action (extracts from the legal opinion here). On October 1 2020 the Commission announced that it would start the legal process of an infringement proceeding against the UK, by sending a letter to the UK and giving it a month to reply (for details of the process, see here). The UK government did not reply in time. However, in December 2020 the UK dropped the disputed provisions from the bill. On 15 June 2022, the Commission resumed infringement proceedings, and opened two new proceedings, following the UK government's proposed bill on the Northern Ireland protocol. The agreement on the Windsor Framework in 2023 settled the dispute. 

In March 2021, the EU Commission began possible legal proceedings regarding an alleged breach of the Northern Ireland Protocol by the UK (see the analysis by David Allen Green). The UK replied to the infringement proceedings letter in May 2021 (see summary of the UK reply here). In the meantime, Raymond McCord filed a case in the EU General Court against the Commission measure invoking the safeguard clause in the Protocol (which never entered into force). This case was dismissed by the EU General Court in December 2021. (On the background to this case, see again an analysis by David Allen Green).

Legal challenges against the protocol were also brought before UK courts. A hearing began in May 2021 (see Twitter thread on the EU law points here; on the UK government position see here). On 30 June 2021 the first instance court ruled that this judicial review was unsuccessful (summary of judgment in Allister and others here; full text of judgment here; see also the analysis by Sarah Kay), The applicants appealed to the Northern Ireland Court of Appeal, which rejected the appeal in March 2022 (see full text and summary of the judgment; and analysis by Anurag Deb).  The Court of Appeal sent questions to the Supreme Court as regards this case in April 2022, and the Supreme Court held a hearing in late 2022. On February 8 2023 the Supreme Court rejected the challenge to the protocol (see analysis here and here). 

The agriculture minister in the Northern Ireland government refused to carry out some of the checks required under the Protocol. The Northern Ireland High Court ruled in December 2022 that this was unlawful (see judgment full text, or the summary of the judgment). 

The Northern Ireland High Court also ruled on the rights provisions of the Protocol, as regards UK citizenship issues, in September 2021 (Chuinneagain), and, as regards abortion, in February 2022 (SPUC; see analysis by Colin Murray; the judgment was upheld on appeal). Subsequent challenges have been decided as regards aspects of asylum law:first Angesom, discussed here; secondly, two judicial reviews of the Illegal Immigration Act (from an individual, and by the NI Human Rights Commission), decided in May 2024 (see initial discussion here, and discussion of the judgment here). The government has announced that it will appeal this judgment. The Northern Ireland High Court has also ruled in Dillon in 2024 that the legislation quashing investigations into Troubles crimes is invalid, due to breach of the protocol (see analysis of the judgment here, and summary of the judgment here).

An order from the Northern Ireland agriculture minister to cease checks under the protocol in February 2022 was challenged, and is suspended pending a court hearing.  Another case (JR83) argued that the Prime Minister acted in bad faith, and did not intend to implement the withdrawal agreement. Leave to bring this judicial review was refused by the Northern Ireland High Court in December 2020, on the grounds that this issue was academic and not suitable for judicial scrutiny. The Northern Ireland Court of Appeal rejected an appeal in August 2021 (summary of the judgment; full text of the judgment).

b) Citizens' rights

On the UK side, the High Court ruled in March 2021 on the arrangements to be made for children in care. In June 2021, the High Court ruled that some non-EU carers of British children had wrongly been excluded from applying for settled status. In April 2021, the High Court refused leave to challenge (for the time being) the 'digital-only' documentation status of EU citizens in the UK. This claim argued a breach of the UK's Equality Act, not of the withdrawal agreement (see comments on the Free Movement blog). The issue of the immigration exemption from the Data Protection Act, also not linked to the withdrawal agreement expressly, has been litigated: the High Court rejected the challenge in October 2019 (Open Rights Group and the 3million), but the appeal to the Court of Appeal was successful (judgment of 26 May 2021), finding that the immigration exception breached the GDPR. Finally, the Independent Monitoring Authority (IMA) lodged a judicial review against the Home Office in December 2021 for allegedly breaching the withdrawal agreement as regards loss of status. In June 2022, permission for judicial review was granted. The High Court ruled against the Home Office on 21 December 2022 (see also the summary of the judgment, by the IMA). The Home Office withdrew an appeal against the judgment. 

On the EU side, a CJEU judgment in July 2021 (see also the Advocate-General's opinion of 24 June 2021), while not about the withdrawal agreement as such, addresses the question of pre-settled EU citizens' access to EU benefits. The CJEU has also been asked to rule on the social security rules in the agreement. 

c) Separation rules

In October 2021, the General Court ruled that a decision about registration of an EU trade mark made  by the EU Intellectual Property Office during the transition period still had to take into account the position of the UK market (Indo European Foods; see also the judgments in Brownie, para 19, and MUSIKISS, paras 29-37, which concerned EU trade mark decisions adopted before the UK left the EU, and the continued application of EU trade mark law to the UK during the transition period). The EU Intellectual Property Office has appealed this judgment to the CJEU; the Court has allowed the appeal to proceed, but has not yet ruled on the merits. 

d) Retained EU law 

The Court of Appeal has ruled on issues relating to, for example, copyright (TuneIn), air passengers' rights (Lipton) and pensions in the event of insolvent employers (Hughes). For a summary of case law on retained EU law as of January 2022, see Jack Williams in the EU Relations blog.

e) UK lawyers

A ruling of the EU General Court in June 2022 summarises when UK lawyers can, and cannot, appear before that Court post-Brexit. Note that there are other cases (citizens' rights, the NI and Cyprus protocols, the financial settlement) when UK lawyers can appear before the CJEU.

12           Trade and Cooperation Agreement

Shellfish companies have threatened legal action against the UK government as regards damage to their exports. The UK government has complained to the EU as regards the same issue. The Court of Appeal judgment in Heathrow Airport v HMT (21 May 2021) discusses both the TCA and the legal effect of WTO law in the UK post-Brexit. A legal challenge to the UK/Morocco trade deal by the Western Sahara Campaign has been given permission to proceed.

The lower courts in Ireland rejected an argument that Ireland had to opt in to the extradition provisions of the treaty, but the Supreme Court of Ireland decided to refer the issue to the CJEU in July 2021 (Case C-479/21). The CJEU agreed to fast-track the case in August, and held a hearing on September 27 2021; an Advocate-General's opinion was released on 9 November 2021; and the CJEU judgment on 16 November 2021 confirmed that Ireland was bound by these provisions and no opt in process was necessary (see analysis here). A parallel legal challenge in the EU General Court to the validity of the decision provisionally applying the TCA, as far as extradition from Ireland to the UK is concerned (Case T-157/21), was dismissed on 18 November 2021 due to lack of standing. Another case asking questions about extradition to the UK was referred to the CJEU in early 2024.

A direct challenge against the TCA concerning visas for British service providers (Case T-442/21 Thomas and Julien v Council) was also dismissed due to lack of standing, on 24 February 2022; an appeal against this ruling to the CJEU is pending.

13           Miscellaneous

The Irish High Court ruled in March 2024 (full text here) that the Irish government unlawfully designated the UK as a 'safe third country' for the purposes of asylum law - although the Irish government plans legislation on the issue (which might be challenged afresh). See discussion here.

The EU courts have also been asked to rule on the impact of Brexit on employment contracts of a UK citizen with the EU administration (a hearing was due on 9 December 2021), and on the position of the CJEU Advocate-General linked to the UK. On the first point, the EU General Court ruled in October 2020 that a UK official who obtained Belgian nationality to stay working with the EU institutions could no longer claim a right to an expatriation allowance. He has appealed to the CJEU; an Advocate-General's opinion on the appeal (supporting his argument) was released 7 April 2022. However, the CJEU dismissed his appeal in September 2022.

On the second point, in September 2020, a judge in the EU General Court suspended the appointment of the replacement for the Advocate-General until the third case, which directly challenged the appointment of her replacement, could be heard (see discussion here). However, on appeal the CJEU overruled this suspension, and the Advocate-General was replaced. In October 2020, the EU General Court dismissed all three of the cases brought by the former Advocate-General: see here, here and here. She appealed these rulings to the CJEU in December 2020: see here and here. The Court of Justice ruled against her appeal on 16 June 2021 (see here and here).

Updates: 27 July 2020: clarified what the Webster judgment ruled in s 3; links to Dutch court rulings added in s 10. 28 July 2020: added reference to English version of July 2020 Shindler judgment in s 10. 6 Sept 2020: updated s 12 on litigation re Advocate-General; s 10 Walker judgment was not appealed. 10 Sept 2020: updated s 11 on possible litigation on internal market bill; updated s 12 re Advocate General. 1 Oct 2020: updated s 10 on EU citizenship case in the French courts, and s 11 on start of litigation process re the internal market bill. 19 Oct 2020: updated s 12 on litigation on Advocate-General nominated by the UK. 3 Nov 2020: updated s 9 on extension of UK membership and s 11 on the withdrawal agreement/internal market bill). 23 Nov 2020: updated s 10 on UK citizens and EU citizenship. 15 Dec 2020: updated s 4 on withdrawal process, s 10 on UK citizens and EU citizenship and s 11 on internal market bill. 16 Dec 2020: updated s 12 on staff member of EU institutions. 21 Dec 2020: updated s 12 on Advocate-General. 31 Jan 2021, 8 Feb 2021: updated s 10 on EU citizenship. 1 April 2021: updated s 10 on EU citizenship, s 11 on withdrawal agreement; added new s 12 on Trade and Cooperation Agreement. 13 April 2021: updated s 11 on withdrawal agreement. 20 April 2021: updated s 7 on devolution. 10 May 2021: updated s 5 on UK status and s 11 on withdrawal agreement (EU citizens). 17 and 18 May 2021: updated s 2 (link to McCord NI High Court judgment); and s 11 on withdrawal agreement (developments in NI Protocol cases). 26 May 2021: updated s 11 (Open Rights/3 Million judgment, Court of Appeal) and s 12 (Heathrow Airport judgment). 10 June 2021: updated s 10 (Price ruling) and s 11 (judgment on carers); corrected summary of Webster judgment in s 3. 14 June 2021: updated s 10 (link to Price ruling; Shindler and Silver rulings made public) and s 12 (Irish extradition cases). 17 June 2021: updated s 13 (link to Sharpston rulings). 28 June 2021: updated s 11 (link to summary of McCord case; opinion on EU citizens' access to benefits). 29 June 2021: updated s 7 (Welsh govt litigation) and s 11 (Western Sahara case). 30 June 2021: updated s 11 (Allister judgment). 28 July 2021: updated s 11 (cases on benefits and pensions) and s 12 (legal challenges to TCA). 16 August 2021: updated s 10 (appeals in cases concerning EU citizenship). 18 August 2021: updated s 10 (appeals in cases concerning EU citizenship) and s 12 (extradition and TCA: case fast-tracked). 1 September 2021: s 11 (JR83 case loses appeal). 9 October 2021: s 12 (extradition and TCA: case update). 28 Oct 2021: s 11 (NI protocol litigation update). 8 Nov 2021: s 12 (challenge to TCA  by British citizens update). 9 Nov 2021: s 12 (update re Irish extradition to UK). 16 Nov 2021: s 12 (Irish extradition judgment); s 13 (hearing on UK staff member). 28 Nov 2021: s 12 (update re Irish extradition to UK). 14 Dec 2021: s 10 (AG opinion date on retaining EU citizenship); s 11 (judicial review of implementation of citizens' rights rules). 20 Dec 2021: s 11 (dismissal of case on Article 16 of NI protocol). 22 Dec 2021: s 11 (possible judicial review of implementation of protocol). 8 Feb 2022: s 11 (NI protocol cases update; retained law blog post). 28 Feb 2022: s 10 (AG opinion on UK nationals retaining EU citizenship). 1 March 2022: s 12 (Julien case dismissed). 15 March 2022 (Welsh government case dismissed; NI Court of Appeal ruling on protocol challenge; date of AG opinion on EU staff case). 19 March 2022, s 11 (plan to appeal in NI protocol case). 25 April 2022, s 11 (citizens' rights case; Supreme Court reference on NI protocol case); 11 May 2022, s 11 (updated links to judgments on the NI protocol and analysis of them) and s 13 (staff cases). 27 May 2022: s 10 (date of judgment on Brits retaining EU citizenship); s 11 (sub-headings added, and case law on EU trade marks added). 13 June 2022: s 10 (judgment on Brits retaining EU citizenship). 15 June 2022: s 11 (infringement proceedings re protocol). 28 June 2022: s 11 (UK lawyers' appearance rights). 30 June 2022: s 11 (citizens' rights). 15 Nov 2022: s 10 (loss of EU citizenship), s 13 (miscellaneous). 5 Dec 2022: s 10 (loss of EU citizenship; new case) and s 11 (Supreme Court hearing). 21 Dec 2022: s 11 (EU citizens in UK - High Court judgment and NI protocol - NI High Court judgment). 18 Jan 2023: s 11 (full text of judgment on NI protocol) and s 12 (Julien case appealed). 8 Feb 2023: s 11 (NI protocol judgment, UK Supreme Court). 16 May 2023: s 10 (judgments due date on UK citizens and EU citizenship), s 11 (litigation on EU citizens in UK). 29 April 2024: s 10 (UK citizens), 11 (NI protocol), 12 (extradition) and 13 (Irish court judgment on asylum). 30 April 2024: s 11 and 13 (links to blog post). 15 May 2024: s 11.a (Windsor Framework - Illegal Migration Act judgment)

Barnard & Peers: chapter 27

Photo credit: Tom Morris, via Wikimedia Commons