5.18. However, the above does not automatically mean that plaintiffs could also foresee that this could lead to the loss of, among other things, their right to live and work in other EU member states. Before the UK expressed its wish, no other Member State had made use of the possibility of withdrawing from the EU under Article 50 TEU. Only when this wish was made known, at least after the outcome of the referendum had become known, could the claimants take into account the possibility that their rights and freedoms as nationals of an EU Member State as referred to in Article 20 TFEU, as a the result of that exit, would be lost. That moment is only a short time ago. In these circumstances, it can not be ruled out that the rights and freedoms that UK citizens living in another EU country derived from Article 20 TFEU should be regarded as acquired rights in the sense referred to above in 5.15 and 5.16.

Broad interpretation of EU citizenship and rights deriving therefrom
5.19. The CJEU has broadly interpreted both EU citizenship and the resulting rights. While Article 20 TFEU states that citizenship of the Union comes alongside national citizenship, the CJEU has ruled that citizenship of the Union should be the primary status of nationals of the EU Member States and that, on that basis, subject to explicit legal exceptions, are entitled to equal treatment in law. (See ECJ 20 September 2001, C-184/99, ECLI: EU: C: 2001: 458 (Grzelczyk), ECJ 11 July 2002, C-224/98, ECLI: EU: C: 2002: 432 (D’Hoop ), CJEU 22 December 2010, C-208/09, ECLI: EU: C: 2010: 806 (Wittgenstein), CJEU 12 May 2011, C-391/09, ECLI: EU: C: 2011: 291 (Runevič Vardyn and Wardyn)).

5.20. Once lawfully acquired, EU citizenship is an independent source of rights and obligations that can not be simply reduced or affected by national government action (see AG Maduro’s conclusion of 30 September 2009 in case C-135/08 (Rottman), under 23 and the recent judgment of the CJEU 14 November 2017, C-165/16, ECLI: EU: C: 2017: 862 (Toufik Lounes)). In the former procedure, the CJEU considered, with regard to the withdrawal of the nationality of a citizen of an EU Member State, that an assessment of the principle of proportionality should take place. Whether the proportionality test must always be carried out individually or can also take place in abstracto, as the basis for a statutory regulation, is the subject of a Dutch question currently pending before the CJEU (ABRvS 19 April 2017, ECLI: NL: RVS : 2017: 1098).

5.21. It is admitted that the cited case law of the CJEU relates to national measures that brought the loss of nationality of a Member State and thereby EU citizenship. Thus, that case-law does not automatically apply to the present case, in which a Member State intends to leave the EU, as a result of which all citizens of that Member State, including those who voted against that intention, are threatened with losing the status of EU citizen. Nevertheless, it is arguable that that case-law, and the principles on which it is based, applies in the same way to the present question, or at least influences the answer to that question.

Protection of the minority against the majority
5.22. The notification referred to in 2.1 above and the negotiations mentioned in 2.2 have taken place as a result of the wish of the majority of those who participated in the Brexit referendum referred to in 2.1. That is in itself entirely in accordance with the way in which a democratic constitutional state functions. But as considered in 5.8 above, the essence of a democratic constitutional state is that the rights and interests of minorities are protected as much as possible. The same applies to the functioning of the EU as a whole which forms a democratic community of (member) states governed by the rule of law.

Solidarity between EU citizens and between them and the Member States
5.23. In view of the case law mentioned above in 5.19, the EU citizenship acquired through the operation of Article 20 TFEU – a new, transnational form of citizenship – aims to unite the (citizens of the) EU Member States and increase their mutual solidarity. Taking into account what has been considered above in 5.21, it can then be argued that this solidarity means that (the citizens of) other EU Member States cannot leave the claimants who, against their will are threatened with losing fundamental rights and freedoms that are derived from that EU, should not be left out in the cold.

Complications in the case of young children who are EU citizens
5.24. In the above it should be borne in mind that the status of EU citizen not only affects the fundamental rights of the relevant EU citizens, but is also important in some circumstances for the right of residence of third-country nationals, provided that is a dependency relationship between the EU citizen and the third-country national and the non-granting of a right of residence to the third-country national would effectively lead to the EU citizen not enjoying effective enjoyment of the rights conferred on him by Article 20 paragraph 2 of the TFEU. According to the CJEU, in any event, that is the case if a third-country national – as in the opinion of the UK after Brexit, if the negotiating parties do not agree otherwise – is denied the right to reside in the Member State in which are his/her young children who are EU citizens. The consequence of a refusal to grant a right of residence to a third-country national would then actually lead to the obligation that EU minor citizens would also be forced to leave the EU (CJEU 8 March 2011, C-34/09, ECLI). : EU: C: 2011: 124 (Ruiz Zambrano) and CJEU 10 May 2017, C-133/15, ECLI: EU: C: 2017: 354 (Chavez-Vilchez)). In addition, it should be noted that, where the dependency relationship does not force the acceptance of a derived right of residence, it can not be claimed on the basis of the importance that the unity of the family must be preserved as much as possible, the CJEU has repeatedly ruled (see CJEU 15 November 2011, C-256/11, ECLI: EU: C: 2011: 734 (Dereci), CJEU 6 December 2012, C-356 and 357/11, ECLI: EU: C: 2012: 776 (O ea) and CJEU May 8, 2013, C-87/12, ECLI: EU: C: 2013: 291 (Ymeraga)).

Result
5.25. What has been considered above in 5.15-5.24 entails that there is reason to doubt the correctness of the interpretation of Article 20 TFEU that the loss of the status of citizen of an EU Member State leads to loss of EU citizenship as well (see for this in 5.14). The answer to the question which explanation is the right one is essential for the assessment of these claims.

Questions referred
1. Does the withdrawal of the United Kingdom from the EU automatically lead to the loss of the EU citizenship of British nationals and thus to the elimination of the rights and freedoms deriving from EU citizenship, if and in so far as the negotiations between the European Council and the United Kingdom are not otherwise agreed?

2. If the answer to the first question is in the negative, should conditions or restrictions be imposed on the maintenance of the rights and freedoms to be derived from EU citizenship?

[This short unofficial summary has been prepared by Bureau Brandeis, the law firm acting for the Claimants]