4) Recitals 10 and 12 of the Framework Decision are worded as follows:

‘(10) The mechanism of the European arrest warrant is based on a high level of confidence between Member States. Its implementation may be suspended only in the event of a serious and persistent breach by one of the Member States of the principles set out in [Article 2 TEU], determined by the Council pursuant to [Article 7(2) TEU] with the consequences set out in [Article 7(3) TEU].

...

(12) This Framework Decision respects fundamental rights and observes the principles recognised by [Articles 2 and 6 TEU] and reflected in the Charter of Fundamental Rights of the European Union ... in particular Chapter VI thereof. Nothing in this Framework Decision may be interpreted as prohibiting refusal to surrender a person for whom a European arrest warrant has been issued when there are reasons to believe, on the basis of objective elements, that the said arrest warrant has been issued for the purpose of prosecuting or punishing a person on the grounds of his or her sex, race, religion, ethnic origin, nationality, language, political opinions or sexual orientation, or that that person's position may be prejudiced for any of these reasons.’

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63 Since these proceedings are, for the parties to the main proceedings, a step in the action pending before the national court, the decision on costs is a matter for that court. Costs incurred in submitting observations to the Court, other than the costs of those parties, are not recoverable. 63) On those grounds, the Court (First Chamber) hereby rules: Article 50 TEU must be interpreted as meaning that mere notification by a Member State of its intention to withdraw from the European Union in accordance with that article does not have the consequence that, in the event that that Member State issues a European arrest warrant with respect to an individual, the executing Member State must refuse to execute that European arrest warrant or postpone its execution pending clarification of the law that will be applicable in the issuing Member State after its withdrawal from the European Union. In the absence of substantial grounds to believe that the person who is the subject of that European arrest warrant is at risk of being deprived of rights recognised by the Charter of Fundamental Rights of the European Union and Council Framework Decision 2002/584/JHA of 13 June 2002 on the European arrest warrant and the surrender procedures between Member States, as amended by Council Framework Decision 2009/299/JHA of 26 February 2009, following the withdrawal from the European Union of the issuing Member State, the executing Member State cannot refuse to execute that European arrest warrant while the issuing Member State remains a member of the European Union.

24) The referring court states that RO has identified four aspects of EU law which might theoretically be engaged, namely: – the right to a deduction of a period spent in custody in the executing Member State, provided for in Article 26 of the Framework Decision; – the so-called ‘specialty’ rule, the subject of Article 27 of the Framework Decision; – the right limiting further surrender or extradition, the subject of Article 28 of the Framework Decision, and – respect for the fundamental rights of the person surrendered under the Charter of Fundamental Rights of the European Union (‘the Charter’).

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26 In those circumstances, the High Court decided to stay the proceedings and to refer the following questions to the Court for a preliminary ruling:

‘(1) Having regard to:

– (a) the giving by the United Kingdom of notice under Article 50 [TEU];

– (b) the uncertainty as to the arrangements which will be put in place between the European Union and the United Kingdom to govern relations after the departure of the United Kingdom; and

– (c) the consequential uncertainty as to the extent to which [RO] would, in practice, be able to enjoy rights under the Treaties, the Charter or relevant legislation, should he be surrendered to the United Kingdom and remain incarcerated after the departure of the United Kingdom,

Is a requested Member State required by European Union Law to decline to surrender to the United Kingdom a person the subject of a European arrest warrant, whose surrender would otherwise be required under the national law of the Member State,

(i) in all cases?

(ii) in some cases, having regard to the particular circumstances of the case?

(iii) in no cases?

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40) The Court has thus acknowledged that, subject to certain conditions, the executing judicial authority has the power to bring the surrender procedure established by the Framework Decision to an end where that surrender may result in the requested person being subject to inhuman or degrading treatment within the meaning of Article 4 of the Charter (judgments of 5 April 2016, Aranyosi and Căldăraru, C‑404/15 and C‑659/15 PPU, EU:C:2016:198, paragraph 104, and of 25 July 2018, Minister for Justice and Equality (Deficiencies in the System of Justice), C‑216/18 PPU, EU:C:2018:586, paragraph 44).

41) For that purpose, the Court has relied, first, on Article 1(3) of the Framework Decision, which provides that that decision is not to have the effect of modifying the obligation to respect fundamental rights and fundamental legal principles as enshrined in Articles 2 and 6 TEU and, second, on the absolute nature of the fundamental right guaranteed by Article 4 of the Charter (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 45).

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43) However, RO argues that, because of the notification by the United Kingdom of its intention to withdraw from the European Union pursuant to Article 50 TEU, he is exposed to the risk that a number of the rights he enjoys under the Charter and the Framework Decision may no longer be respected after the withdrawal of the United Kingdom from the European Union. According to RO, the principle of mutual trust, which is at the basis of mutual recognition, has been irreparably eroded by that notification, and consequently the surrender provided for by the Framework Decision ought not to be executed.

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50) As regards the fundamental rights enshrined in Article 4 of the Charter, which correspond to those stated in Article 3 of the ECHR (judgment of 5 April 2016, Aranyosi and Căldăraru, C‑404/15 and C‑659/15 PPU, EU:C:2016:198, paragraph 86), in a situation where the referring court were to consider, as appears to be the case, given the wording of the questions referred for a preliminary ruling and the documents sent to the Court, that the information received enables it to discount the existence of a real risk that RO will suffer, in the issuing Member State, inhuman or degrading treatment, within the meaning of Article 4 of the Charter, it would not be appropriate, as a general rule, to refuse to surrender him on that basis, without prejudice to RO’s opportunity, after surrender, to have recourse, within the legal system of the issuing Member State, to legal remedies that may enable him to challenge, where appropriate, the lawfulness of the conditions of his detention in a prison of that Member State (see, to that effect, judgment of 5 April 2016, Aranyosi and Căldăraru, C‑404/15 and C‑659/15 PPU, EU:C:2016:198, paragraph 103).

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52) In that regard, it must be observed that, in this case, the issuing Member State, namely the United Kingdom, is party to the ECHR and, as stated by that Member State at the hearing before the Court, it has incorporated the provisions of Article 3 of the ECHR into its national law. Since its continuing participation in that convention is in no way linked to its being a member of the European Union, the decision of that Member State to withdraw from the Union has no effect on its obligation to have due regard to Article 3 of the ECHR, to which Article 4 of the Charter corresponds, and, consequently, cannot justify the refusal to execute a European arrest warrant on the ground that the person surrendered would run the risk of suffering inhuman or degrading treatment within the meaning of those provisions.

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59) Since the rights resulting from Articles 26 to 28 of the Framework Decision and the fundamental rights laid down in Article 4 of the Charter are protected by provisions of national law in cases not only of surrender, but also of extradition, those rights are not dependent on the application of the Framework Decision in the issuing Member State. It therefore appears, though subject to verification by the referring court, that there is no concrete evidence to suggest that RO will be deprived of the opportunity to assert those rights before the courts and tribunals of that Member State after its withdrawal from the European Union.

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62) The answer to the questions referred is, therefore, that Article 50 TEU must be interpreted as meaning that mere notification by a Member State of its intention to withdraw from the European Union in accordance with that article does not have the consequence that, in the event that that Member State issues a European arrest warrant with respect to an individual, the executing Member State must refuse to execute that European arrest warrant or postpone its execution pending clarification of the law that will be applicable in the issuing Member State after its withdrawal from the European Union. In the absence of substantial grounds to believe that the person who is the subject of that European arrest warrant is at risk of being deprived of rights recognised by the Charter and the Framework Decision following the withdrawal from the European Union of the issuing Member State, the executing Member State cannot refuse to execute that European arrest warrant while the issuing Member State remains a member of the European Union.

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63) Since these proceedings are, for the parties to the main proceedings, a step in the action pending before the national court, the decision on costs is a matter for that court. Costs incurred in submitting observations to the Court, other than the costs of those parties, are not recoverable.

On those grounds, the Court (First Chamber) hereby rules:

Article 50 TEU must be interpreted as meaning that mere notification by a Member State of its intention to withdraw from the European Union in accordance with that article does not have the consequence that, in the event that that Member State issues a European arrest warrant with respect to an individual, the executing Member State must refuse to execute that European arrest warrant or postpone its execution pending clarification of the law that will be applicable in the issuing Member State after its withdrawal from the European Union. In the absence of substantial grounds to believe that the person who is the subject of that European arrest warrant is at risk of being deprived of rights recognised by the Charter of Fundamental Rights of the European Union and Council Framework Decision 2002/584/JHA of 13 June 2002 on the European arrest warrant and the surrender procedures between Member States, as amended by Council Framework Decision 2009/299/JHA of 26 February 2009, following the withdrawal from the European Union of the issuing Member State, the executing Member State cannot refuse to execute that European arrest warrant while the issuing Member State remains a member of the European Union.