A New York state appeals court ruled on Tuesday that Facebook had no legal standing to challenge search warrants on behalf of its customers, a decision that dealt a blow to civil libertarians and social media companies seeking to expand Internet privacy, reports the New York Times.

Upholding a lower court decision, the five-judge panel in Manhattan said that under state and federal law only a defendant can challenge a search warrant, and it must be done during a hearing before trial. At that point, defendants can move to have evidence thrown out as the fruit of an illegal search.

But Facebook, as the online entity storing material, does not have the power to ask a judge to throw out search warrants before they have been executed, said Judge Dianne T. Renwick, who wrote the unanimous opinion. “There is no constitutional or statutory right to challenge an allegedly defective warrant before it is executed,” she wrote.

Judge Renwick rejected Facebook’s argument that it should be able to challenge what it sees as illegal searches of its customers’ files. The company argued that such warrants differ from physical searches of an office or a home, since Facebook must perform the task for the police. As a result, the company contended, search warrants served on social media sites are akin to civil subpoenas for records, which may be challenged in court.

The case — known formally as “In Re 381 Search Warrants Directed to Facebook Inc.” — has been closely watched as a test case by civil libertarians and other social media companies. Several tech giants, including Google, LinkedIn and Twitter, have filed amicus briefs. So has the New York Civil Liberties Union.

The judges said that in their reading, the federal Stored Communications Act allows Internet service providers to object to subpoenas and court orders, but not to search warrants.