I read this Article: https://www.theguardian.com/technolo...bers-user-data

Summary:
The German data protection agency has ordered Facebook to stop collecting user data from its WhatsApp messenger app and delete any data it has already received.

A Facebook spokesperson said: “Facebook complies with EU data protection law. We will work with the Hamburg DPA in an effort to address their questions and resolve any concerns.”

Question:

I'm wondering which article(s) of the EU protection law is enforced? Or where is a good place that kind of case law?