A German data protection watchdog has told Facebook that it can't force people to use their real names. The Hamburg data protection authority, which is responsible for policing Facebook in Germany, said that the company could not unilaterally change accounts under pseudonyms to their users' real names, nor could it ask them for official ID or block them.

The order came in response to a case where a woman complained to the Hamburg watchdog after Facebook blocked her account for using a pseudonym, requested a copy of her ID and unilaterally changed her username into her real name. The German data authority said the woman did not want to use her real name to avoid being contacted through it for business matters.

Facebook said it was disappointed its name policy is being revisited after German courts had previously found it was compliant with the European Union laws. “The use of authentic names on Facebook protects people’s privacy and safety by ensuring people know who they’re sharing and connecting with,” the company said in an e-mailed statement.

Facebook argued, as it has done in the past, that as its European headquarters are in Ireland it should only abide by Irish law in Europe and consequently has rejected the jurisdiction of other national authorities. A 2011 audit by an Irish privacy watchdog reportedly found that Facebook’s policy was in line with local laws.

Johannes Caspar, Hamburg’s data regulator, has refuted this claim that Facebook should only be subject to Irish data protection laws. "For that matter Facebook cannot again argue that only Irish Data Protection law would be applicable [...] anyone who stands on our pitch also has to play our game," he said.