Data subjects versus Supervisory Authority – Court Ruling (Germany, 2026)

A district (the controller), acting as the lower water authority, initiated administrative proceedings after identifying unauthorised riverbank works and a private jetty on two riverside properties. One property belonged to a water utility company, while the other belonged to a municipality and was leased to the data subjects. During those proceedings, the controller shared the data subjects' personal data with various participants, including the owners of the affected properties, other public authorities and a lawyer who claimed to represent the data subjects. The data subjects lodged a complaint with the competent supervisory authority (LDI NRW), alleging that the controller had unlawfully processed and disclosed their personal data. They argued that their personal data had been shared with uninvolved third parties, that the controller had communicated with a lawyer whom they had not authorised, recorded a telephone conversation with an unknown person, and transmitted personal data by unencrypted email. The controller's data protection officer addressed each allegation and provided additional factual information concerning the disputed processing operations. The DPA initially informed the data subjects that no GDPR infringement was apparent, invited them to provide any additional factual information, and explained that it would obtain extracts from the controller's administrative file if there were concrete indications that it contained relevant facts not already available. The data subjects did not identify any additional facts and instead reiterated their legal position that the controller had breached its GDPR accountability obligations. The DPA rejected the complaint, concluding that no GDPR infringement could be established. The data subjects then brought an action before the Verwaltungsgericht Düsseldorf (Administrative Court Düsseldorf), seeking a fresh decision on their complaint on the basis that the DPA had failed to adequately investigate the complaint because it had not obtained the controller's administrative file before reaching its decision. The court held that Articles 57(1)(f) and 77(1) GDPR give rise to an enforceable right requiring a supervisory authority to investigate a complaint to the extent appropriate in the circumstances before determining whether a GDPR infringement has occurred. Recital 141 GDPR requires the investigation to extend as far as is appropriate in light of the circumstances of the individual case, including the significance of the complaint and the seriousness of the alleged infringement. Applying these principles, the court held that the DPA had adequately investigated the complaint. It had considered each allegation together with the detailed response provided by the controller's data protection officer, invited the data subjects to provide any additional factual information, and explained that it would obtain extracts from the administrative file if concrete indications emerged that further relevant facts required clarification. As the data subjects did not provide any additional facts and there were no objective indications that the information already available was inaccurate or incomplete, the court held that the DPA was not required to obtain the controller's administrative file or undertake further investigations in the absence of concrete indications that additional factual clarification was necessary. The court further held that the DPA had correctly concluded that no GDPR infringement had occurred. The court held that the disputed processing was lawful under Article 6(1)(e) GDPR, read together with Article 6(3) GDPR and § 88 of the German Water Resources Act (WHG), which provided the legal basis for the processing. The court also held that the transmission of personal data by email did not infringe Article 5(1)(f) GDPR because, in the circumstances of the case, transport encryption provided an appropriate level of security.