Case C-398/19: Judgment of the Court (Grand Chamber) of 17 December 2020 (request for a preliminary ruling from the Kammergericht Berlin — Germany) — Proceedings relating to the extradition of BY (Reference for a preliminary ruling — Citizenship of the European Union — Articles 18 and 21 TFEU — Extradition of a Union citizen to a third State — Person acquiring Union citizenship after transferring the centre of his or her interests to the Member State from which extradition is requested — Scope of EU law — Prohibition on extradition applied solely to own nationals — Restriction on freedom of movement — Justification based on the prevention of impunity — Proportionality — Information to the Member State of which the requested person is a national — Obligation on the Member State from which extradition is requested and the Member State of origin to ask the third State requesting extradition to send the criminal investigation file — No obligation)