In extradition proceedings, the reciprocity condition is satisfied when the requesting State provides an assurance of substantially equivalent treatment — formal diplomatic notes from the Chinese Embassy confirming no restrictions on Italy's participation in passive extradition proceedings are sufficient to this end. The legitimacy of a sub-state authority to represent the requesting State is confirmed by the Embassy and cannot be challenged under the requested State's domestic law. Any authority empowered under the requesting State's internal law to act in extradition proceedings must be recognized as a procedural party. Under Article 702 of the Italian Code of Criminal Procedure, the only formal requirement for the requesting State's intervention is the appointment of a lawyer admitted to practice before Italian courts, with no further formalities prescribed. A distinction must be drawn between mere participation in the proceedings — which requires only an explicit expression of interest — and full procedural standing as a party, which requires the appointment of counsel and confers the right to participate in oral argument and to lodge an independent appeal before the Court of Cassation.