Yelp, the online business review site, has to identify the real identities of users that posted negative comments on the website, a US court has heard.
Joe Hadeed of Hadeed Carpet Cleaning had seven negative reviews on his company's Yelp page that he believed were false and defamatory, so he issued a subpoena to Yelp in a bid to identify the anonymous users, the BBC reports.
But Yelp declined to respond to it, suggesting that anonymous speech was protected by the First Amendment.
However, the Virginia Court of Appeals has agreed with Hadeed that Yelp must identify the users accused of defamation, after stating that Hadeed had provided "sufficient reason" for it to think that the users may not have been customers.
In a statement, the judge said: "Generally, a Yelp review is entitled to First Amendment protection because it is a person's opinion about a business that they patronised."
He stated that users should be able to express their opinions anonymously without having to fear being identified as a result of someone disagreeing with them.
But he added: "If the reviewer was never a customer of the business, then the review is not an opinion; instead the review is based on a false statement [as is therefore not protected by the First Amendment]."
Yelp said that it was trying to convince the State of Virginia to act like other US states by ensuring that online speech is not be stifled by those upset by what has been said.
"We are disappointed that the Virginia Court of Appeals has issued a ruling that fails to adequately protect free speech rights on the internet, and which allows businesses to seek personal details about website users - without any evidence of wrongdoing - in efforts to silence online critics," the firm said in a statement.