While Facebook loves sharing incredibly detailed information about users’ interests and web-browsing habits with marketers, the social media network isn’t so keen on making massive amounts of user info available to prosecutors, presumably because the district attorney’s office isn’t looking to buy ads. Facebook announced last night that it’s currently fighting warrants from authorities in New York who are looking to get data on a group of 381 users.

The company says that the warrants, which represent the largest single demand for user info from the site, seek “nearly all data” from the accounts in question, “including photos, private messages and other information.”

Facebook believes the warrants, all involving a large investigation into allegations of disability fraud, violate Constitutional protections against illegal searches.

“We fought forcefully against these 381 requests and were told by a lower court that as an online service provider we didn’t even have the legal standing to contest the warrants. We complied only after the appeals court denied our application to stay this ruling, and after the prosecutor filed a motion to find us in criminal contempt,” explained Facebook’s deputy general counsel, who says the company was under a gag order for several months that prohibited it from speaking publicly about the warrants, or to notify those affected.

The lower court held that, when looking at a large-scale investigation “the relevance or irrelevance of items seized within the scope of a search warrant may be unclear and require further investigatory steps.”

In an attempt to undo the damage, Facebook took its case to an appellate court last week, arguing that the “vast scope of the government’s search and seizure here would be unthinkable in the physical world.”

While the appeal is still pending, the warrants were subsequently unsealed and Facebook says it has since alerted those users whose information was gathered using the warrants.

Prosecutors defend the warrants, which have thus far resulted in 62 indictments.

“This was a massive scheme involving as many as 1,000 people who defrauded the federal government of more than $400 million in benefits,” a rep for the Manhattan DA’s office tells Ars Technica about the warrants. “The defendants in this case repeatedly lied to the government about their mental, physical, and social capabilities. Their Facebook accounts told a different story. A judge found there was probable cause to execute search warrants, and two courts have already found Facebook’s claims without merit.”

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