Facebook acquired the global messaging service two years ago and announced this summer that WhatsApp would begin sharing the phone numbers of its users with the social network as part of a program to synchronize the two businesses.
However, Hamburg’s Commissioner for Data Protection ruled Tuesday that Facebook “neither has obtained an effective approval from the WhatsApp users, nor does a legal basis for the data reception exist.”
Facebook, whose German operations are based in Hamburg, did not immediately respond to a request for comment.
The California-based company has faced repeated challenges in Germany, where there are strict laws on data privacy and intellectual property.
© Copyright 2016 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.