Court documents unsealed Friday show Google, Yahoo, Facebook, and Microsoft are arguing that government gag orders that stop them from disclosing the number of national security requests they receive violate the companies' First Amendment right to free speech.

Leaks by former National Security Agency contractor Edward Snowden that revealed how the government uses tech firms in its surveillance efforts have damaged their bottom lines and public reputations -- particularly overseas. The companies have begun to push back against some government orders to stay silent.

The gag orders, called "national security letters," compel Web and telecommunication companies to share information with the government while simultaneously prohibiting them from speaking about the request. Since the Snowden leaks, Google, Yahoo, Facebook, and Microsoft have fought to include more information about national security requests in regular reports they release on how much data the government requests from their servers.

In the court documents, filed in April with the 9th Circuit Court in California, the tech giants argue that the government is infringing on their First Amendment rights -- a form of prior restraint. The government has argued that companies have no First Amendment right to share information gained from participation in a secret government investigation, according to the filing.

The case is now on appeal.

The companies do not want to disclose any information that would place specific investigations in jeopardy, the filings note. But they do "wish to publish more detailed aggregate statistics about the volume, scope and type of [national security letters] that the government uses to demand information about their users," and reject the arguments the government has made to justify the gag orders. Many companies have already reached one-time agreements with the government to include broad ranges of how many letters they receive -- such as "0-999" -- in individual reports. They would like to continue this practice without asking for permission each time.

Speech about secret government investigations, the companies say, "is not within any traditionally unprotected category." The companies say there's no precedent for the extent to which the government's gag orders suppress free speech.

"The government attempts to sidestep the serious First Amendment issues raised in this case by arguing that there is no First Amendment right to disclose information gained from participation in a secret government investigation," the companies said. "That is incorrect."

Since the Patriot Act expanded the FBI's ability to use national security letters, privacy advocates and government watchdogs say there has been a marked rise in the use of these letters, though more companies have begun to challenge them in light of the Snowden leaks. On Thursday, Microsoft announced that it had successfully fought a national security letter from the FBI, according to unsealed documents from a different case in Seattle, though the government was able to get the information it wanted by other means.

In a statement, Yahoo said it plans to continue pursuing this issue. "The U.S. Government should allow Yahoo and other tech companies to disclose more about the volume, scope and type of National Security Letters (NSLs) they receive."

Google also said it would continue pushing for greater transparency from the government. "People have the right to know when and how governments request their information," a Google spokeswoman said. "We hope the court recognizes how damaging it can be when laws prevent companies from being open about government actions that can infringe on civil liberties.”

The FBI referred the matter to the Department of Justice, which did not immediately respond to a request for comment; neither did Microsoft and Facebook.