Facebook is fighting a U.S. court order in which it was forced to hand over data belonging to almost 400 people involved in a benefit fraud trial.
The social media site said the request was “by far the largest” it had ever received from a government body.
Photographs, private messages and other information were supplied to a New York court last year, but the process was only made public by a judge this week.
The ruling defined Facebook as a “digital landlord.”
A judge said this definition meant the company must comply with search warrants.
The original case investigated fraudulent claimants of U.S. federal disability benefits, whose Facebook accounts apparently showed that they were in fact healthy.
The web giant was ordered to hand over information from the 381 accounts, which the court said contained “evidence of criminality.”
After an appeal was denied, Facebook complied with the request but protested that it violated the Fourth Amendment of the U.S. Constitution, which protects against “unreasonable searches and seizures.”
Facebook also voiced concerns about the lack of date restrictions on the warrant, which it argued allowed the U.S. government to keep the data indefinitely.
“This unprecedented request is by far the largest we’ve ever received — by a magnitude of more than 10 — and we have argued that it was unconstitutional from the start,” wrote Chris Sonderby, a legal adviser to Facebook.
“Of the 381 people whose accounts were the subject of these warrants, 62 were later charged in a disability fraud case.
“This means that no charges will be brought against more than 300 people whose data was sought by the government without prior notice to the people affected.”
In a summation of the legal justification for the court’s decision, the judge wrote: “Facebook could best be described as a digital landlord, a virtual custodian or storage facility for millions of tenant users and their information.