The Hamburg data protection commissioner, already at odds with Facebook over its use of face recognition technology, reopened its proceedings against the company in August last year, telling the company to either obtain explicit consent for face recognition from users, delete the data, or face a lawsuit, Caspar said at the time.
Facebook turned off facial recognition for all European users in September last year, and said it would delete all face recognition templates for existing users in Europe.
The German commissioner stopped its proceedings against Facebook in February, when it confirmed that the company had deleted the facial recognition data gathered on German users without their consent.
Turning on facial recognition again in Germany might be illegal, Caspar said, adding that it depends on how Facebook implements it. The social network should ask for the explicit and informed consent of the user, Caspar said.
"That means that there has to be offered an opt in for users," he added.
Tag suggest is used in the U.S. in the same way it was used in Europe before it was turned off. Facial recognition software is used to calculate a unique template of a user's appearance based on facial features using variables such as the distance between the eyes, nose and ears.
"We are able to suggest that your friend tag you in a picture by scanning and comparing your friend's pictures to information we've put together from your profile pictures and the other photos in which you've been tagged. You can control whether we suggest that another user tag you in a photo using the 'Timeline and Tagging' settings," the proposed change reads.
However, according to the Irish DPC, Facebook does not yet intend to offer the service in Europe.
The Irish DPC suggested to Facebook Ireland that it clarify to its users that the tag suggest feature is not currently available in Europe, she added.
Facebook is still working with regulators to find a way to turn face recognition back on in Europe, a Facebook Germany spokeswoman said in an email.