Facebook says New York City prosecutors who were building a disabilities-benefits fraud case last year got data from the Facebook accounts of 381 people.
The social media giant disclosed a nearly yearlong legal fight over the issue after the filings were unsealed this week.
Facebook ultimately turned over the information but is appealing the court order that required it to do so.
The Menlo Park, California-based company says prosecutors intruded on users' privacy in obtaining the largest set of search warrants the company has ever received. It says 62 of the users were among 134 people charged in the case.
The Manhattan district attorney's office and a judge have said the search warrants were justified.
The dispute adds to a roster of clashes between authorities and Internet companies.