Lack of access to personal data does not unmake a joint controller
The Court of Justice of the EU decided in Case C-210/16 Wirtschaftsakademie that Facebook and the administrator of a fan page created on Facebook are joint controllers under EU data protection law. That means shared responsibility (with Facebook) to comply with EU data protection law for the processing of personal data occurring through their Facebook Page.
Read full article: The CJEU decides lack of access to personal data does not unmake a joint controller: A look at Wirtschaftsakademie