This story was written by Jennifer Baker.

A senior advisor to Europe's top court is due to decide on Thursday whether, in principle, all Europeans have the right to surf the Internet anonymously.

The European Court of Justice's (CJEU's) advocate general will publish his guidance in a case which German Pirate Party politician and activist, Patrick Breyer, brought against the German government for logging all visits to government websites.

The official opinion—although not legally binding—is usually a good indication of how the court will eventually rule, and in this case could have repercussions for data-hoarding Internet giants such as Google and Facebook.

A number of countries throughout the European Union have requested that website operators disclose any tracked behaviour for the prevention, investigation, detection, and prosecution of criminal offences. Operators themselves may track users activity for commercial purposes.

Breyer wants to see that practice outlawed, and has demanded that operators anonymise users‘ IP addresses.

"Nobody has a right to record everything we do and say online. Generation Internet has a right to access information online just as unmonitored and without inhibition as our parents read the paper, listened to the radio or browsed books," he argued.

Furthermore, Breyer believes such monitoring isn't even effective: "IP addresses have turned out to be extremely prone to error and unreliable when used to identify users."

The advocate general will have to decide whether IP addresses transmitted when a website is accessed do or don't fall under the EU's privacy legislation and whether operators have a "legitimate interest" in recording them along with users' "click stream."

In 2014, the CJEU ruled that obligatory blanket retention of communications under the Data Retention Directive was illegal and disproportionate—even for law enforcement purposes—but even after the EU law was struck down many countries reintroduced their own version.

Update

Late on Thursday afternoon the advocate general Manuel Campos Sanchez's opinion was published (it's yet to be made available in the English language).

The AG said that fixed or static IP addresses are unquestionably personal data. But the more thorny question of whether dynamic IP qualify is at stake. Essentially Sanchez considered whether the addition of information from a third party service provider might make such data sufficient to identify individual Internet users.

He found that dynamic IP addresses—which provide information on date and time of access of a computer (or other device) to a website—combined with certain patterns of behavior of Internet users "constitute a possible interference with the right to and respect for for private life guaranteed in Article 8 of the European Convention for the protection of human rights and fundamental freedoms."

At the centre of his deliberations was whether the authorities might "reasonably" have access to such third party info.