EU data protection (EUDataP) Article 55
1. Each supervisory authority shall be competent for the performance of the tasks assigned to and the exercise of the powers conferred on it in accordance with this Regulation on the territory of its own Member State.
2. Where processing is carried out by public authorities or private bodies acting on the basis of points (c) or (e) of Article 6(1), the supervisory authority of the Member State concerned shall be competent. In such cases Article 56 does not apply.
3. Supervisory authorities shall not be competent to supervise processing operations of courts acting in their judicial capacity.