In addition, the fact that the action in the main proceedings seeks a declaratory remedy does not prevent the Court from ruling on a question referred for a preliminary ruling, provided that the action is permitted under national law and that the question meets an objective need for the purpose of settling the dispute properly brought before the referring court (see, to that effect, judgments of 15 December 1995, Bosman, C‑415/93 , EU:C:1995:463 , paragraph 65 , and of 16 June 2015, Gauweiler and Others, C‑62/14 , EU:C:2015:400 paragraph 28 ). Accordingly, there is indeed a dispute before the referring court, even though the respondent in the main proceedings chose not to address the substance of the issue raised by the petitioners in the main proceedings, maintaining only that the petitioners’ action was inadmissible (see, to that effect, judgment of 8 July 2010, Afton Chemical, C‑343/09 , EU:C:2010:419 , paragraphs 11 and 15 ).

The Court may refuse to rule on a question referred for a preliminary ruling by a national court only where it is quite obvious that the interpretation of EU law that is sought bears no relation to the actual facts of the main action or its purpose, where the problem is hypothetical, or where the Court does not have before it the factual or legal material necessary to give a useful answer to the questions submitted to it (judgments of 16 June 2015, Gauweiler and Others, C‑62/14 , EU:C:2015:400 , paragraph 25 , and of 7 February 2018, American Express, C‑304/16 , EU:C:2018:66 , paragraph 32 ). It is not for the Court to call into question the referring court’s assessment of the admissibility of the action in the main proceedings, which falls, in the context of the preliminary ruling proceedings, within the jurisdiction of the national court; nor is it for the Court to determine whether the order for reference was made in accordance with the rules of national law governing the organisation of the courts and legal proceedings (see, to that effect, judgments of 16 June 2015, Gauweiler and Others, C‑62/14 , EU:C:2015:400 , paragraph 26 , and of 7 February 2018, American Express, C‑304/16 , EU:C:2018:66 , paragraph 34 ). In the present case, the referring court rejected the pleas of inadmissibility raised before it by the United Kingdom Government concerning the hypothetical or academic nature of the action in the main proceedings. It follows that, in so far as the arguments of the United Kingdom Government and of the Commission are intended to call into question the admissibility of that action, they are irrelevant for the purposes of determining whether the request for a preliminary ruling is admissible (see, to that effect, judgment of 13 March 2007, Unibet, C‑432/05 , EU:C:2007:163 , paragraph 33 ).

Article 50 TEU must be interpreted as meaning that, where a Member State has notified the European Council, in accordance with that article, of its intention to withdraw from the European Union, that article allows that Member State — for as long as a withdrawal agreement concluded between that Member State and the European Union has not entered into force or, if no such agreement has been concluded, for as long as the two-year period laid down in Article 50(3) TEU, possibly extended in accordance with that paragraph, has not expired — to revoke that notification unilaterally, in an unequivocal and unconditional manner, by a notice addressed to the European Council in writing, after the Member State concerned has taken the revocation decision in accordance with its constitutional requirements. The purpose of that revocation is to confirm the EU membership of the Member State concerned under terms that are unchanged as regards its status as a Member State, and that revocation brings the withdrawal procedure to an end.

As regards the context of Article 50 TEU, reference must be made to the 13th recital in the preamble to the TEU, the first recital in the preamble to the TFEU and Article 1 TEU, which indicate that those treaties have as their purpose the creation of an ever closer union among the peoples of Europe, and to the second recital in the preamble to the TFEU, from which it follows that the European Union aims to eliminate the barriers which divide Europe. It is also appropriate to underline the importance of the values of liberty and democracy, referred to in the second and fourth recitals of the preamble to the TEU, which are among the common values referred to in Article 2 of that Treaty and in the preamble to the Charter of Fundamental Rights of the European Union, and which thus form part of the very foundations of the European Union legal order (see, to that effect, judgment of 3 September 2008, Kadi and Al Barakaat International Foundation v Council and Commission, C‑402/05 P and C‑415/05 P, EU:C:2008:461, paragraphs 303 and 304). As is apparent from Article 49 TEU, which provides the possibility for any European State to apply to become a member of the European Union and to which Article 50 TEU, on the right of withdrawal, is the counterpart, the European Union is composed of States which have freely and voluntarily committed themselves to those values, and EU law is thus based on the fundamental premiss that each Member State shares with all the other Member States, and recognises that those Member States share with it, those same values (see, to that effect, judgment of 25 July 2018, Minister for Justice and Equality (Deficiencies in the system of justice), C‑216/18 PPU, EU:C:2018:586, paragraph 35).

In those circumstances, given that a State cannot be forced to accede to the European Union against its will, neither can it be forced to withdraw from the European Union against its will. However, if the notification of the intention to withdraw were to lead inevitably to the withdrawal of the Member State concerned from the European Union at the end of the period laid down in Article 50(3) TEU, that Member State could be forced to leave the European Union despite its wish — as expressed through its democratic process in accordance with its constitutional requirements — to reverse its decision to withdraw and, accordingly, to remain a Member of the European Union. Such a result would be inconsistent with the aims and values referred to in paragraphs 61 and 62 of the present judgment. In particular, it would be inconsistent with the Treaties’ purpose of creating an ever closer union among the peoples of Europe to force the withdrawal of a Member State which, having notified its intention to withdraw from the European Union in accordance with its constitutional requirements and following a democratic process, decides to revoke the notification of that intention through a democratic process.

That conclusion is corroborated by the provisions of the Vienna Convention on the Law of Treaties, which was taken into account in the preparatory work for the Treaty establishing a Constitution for Europe. In the event that a treaty authorises withdrawal under its provisions, Article 68 of that convention specifies inter alia, in clear and unconditional terms, that a notification of withdrawal, as provided for in Article 65 or 67 thereof, may be revoked at any time before it takes effect.

(see paras 61-63, 65-67, 70, 71, 75, operative part)