Articles 18 and 21 TFEU must be interpreted as meaning that, where an extradition request has been made by a third country for an EU citizen who has exercised his right to free movement, not for the purpose of prosecution, but for the purpose of enforcing a custodial sentence, the requested Member State, whose national law prohibits the extradition of its own nationals out of the European Union for the purpose of enforcing a sentence and makes provision for the possibility that such a sentence pronounced abroad may be served on its territory, is required to ensure that that EU citizen, provided that he resides permanently in its territory, receives the same treatment as that accorded to its own nationals in relation to extradition.

As was recalled in paragraph 33 of this judgment, given that extradition is intended to prevent the risk of impunity for nationals of Member States other than the requested Member State, where the national legislation at issue in the main proceedings makes it possible to extradite nationals of Member States other than the Republic of Finland, it is necessary to examine the proportionate nature of that legislation by ascertaining whether there are measures which are equally effective in achieving that objective but which are less prejudicial to the freedom of movement of those nationals (judgment of 6 September 2016, Petruhhin, C‑182/15, EU:C:2016:630, paragraph 41) by taking into account all the factual and legal circumstances of the case.

In that regard, it must be recalled that, in accordance with settled case-law, citizenship of the Union is intended to be the fundamental status of nationals of the Member States (see, inter alia, judgments of 20 September 2001, Grzelczyk, C‑184/99, EU:C:2001:458, paragraph 31; of 8 March 2011, Ruiz Zambrano, C‑34/09, EU:C:2011:124, paragraph 41, and of 5 June 2018, Coman and Others, C‑673/16, EU:C:2018:385, paragraph 30). Every Union citizen may therefore rely on the prohibition of discrimination on grounds of nationality laid down in Article 18 TFEU in all situations falling within the scope ratione materiae of EU law, and those situations include, as in the dispute in the main proceedings, the exercise of the freedom conferred by Article 21 TFEU to move and reside within the territory of the Member States (see judgments of 4 October 2012, Commission v Austria, C‑75/11, EU:C:2012:605, paragraph 39, and of 11 November 2014, Dano, C‑333/13, EU:C:2014:2358, paragraph 59). In addition, although, in the absence of EU legal provisions on the extradition of nationals of Member States to Russia, Member States retain the power to adopt such provisions, those Member States are required to exercise that power in accordance with EU law, in particular, the prohibition on discrimination laid down in Article 18 TFEU and the freedom to move and reside within the territory of the Member States guaranteed by Article 21(1) TFEU.

In view of the aim of preventing the risk of impunity, Finnish nationals, on the one hand, and, on the other, nationals of other Member States who reside permanently in Finland and demonstrate a certain degree of integration into that State’s society are in a comparable situation (see, by analogy, judgment of 6 October 2009, Wolzenburg, C‑123/08, EU:C:2009:616, paragraph 67). Therefore, Articles 18 and 21 TFEU require that nationals of other Member States who reside permanently in Finland and whose extradition is requested by a third country for the purpose of enforcing a custodial sentence should benefit from the provision preventing extradition from being applied to Finnish nationals and may, under the same conditions as Finnish nationals, serve their sentences on Finnish territory.

(see paras 40, 43-47, 50, operative part)