Microsoft on Thursday launched a lawsuit against the US government, arguing that secret warrants to search people's email violates the constitutional rights of Americans.
Microsoft brought the case "because its customers have a right to know when the government obtains a warrant to read their emails, and because Microsoft has a right to tell them," said the court.
The lawsuit said that a requirement to keep silent on warrants on data violates constitutional protection of free speech and safeguards against unreasonable searches.
Federal courts have issued nearly 2,600 secrecy orders in the past 18 months, gagging Microsoft from saying anything about warrants and other legal actions targeting customers' data, according to the filing.
"We believe that with rare exceptions consumers and businesses have a right to know when the government accesses their emails or records," Microsoft chief legal officer, Brad Smith, said.
"Yet it's becoming routine for the US government to issue orders that require email providers to keep these types of legal demands secret. We believe that this goes too far and we are asking the courts to address the situation," he added.
Internet giants have complained that these types of secret search warrants erode trust in US technology companies and violate the rights of citizens and businesses.
The situation has become more urgent as computing and data storage services shift from software packages loaded onto individual computers to servers running on the Internet cloud.
Controversy over spying, security and privacy over the Internet has been heating up in the past decade, boiling over after former US intelligence contractor, Edward Snowden, revealed wide-scale online spying evidence.
Legally, Microsoft took aim at the Electronic Communications Privacy Act, which is used by police to investigate crimes. This act is not used to back National Security Letters that order tech companies to remain mum about search warrants within the framework of the fight against terrorism.
The constitutional arguments against gagged warrant requests in both cases are very similar. If the case results with victory for Microsoft, the result could echo in a challenge to national security letters, the attorney said.