Microsoft Corporation has sued the US government over a federal law that allows authorities to examine customer emails or files without the individual's knowledge.
The lawsuit, filed on Thursday in the federal court in Seattle, argues that the US government is violating the Constitution by abusing a decades-old law, the Electronic Communications Privacy Act (ECPA), to obtain court orders requiring it to access and search customer files stored on its servers, while prohibiting it from notifying the customer.
"Microsoft brings this 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," the company said in the court filing.
According to the suit, the ECPA allows courts to order Microsoft or other email service providers to remain silent about warrants for data on the grounds that tipping people off might hamper investigations.
That power violates constitutional protection of free speech and safeguards against unreasonable searches, Microsoft argued in the suit.
The court filing said federal courts in the past 18 months have issued nearly 2,600 secrecy orders gagging Microsoft from saying anything about warrants and other legal actions targeting customers' data.
This is the fourth recent lawsuit the technology giant has filed against the government on similar privacy issues. In 2013, it publicly vowed to challenge many of the secrecy orders for its business customers.
"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 in a blog.
"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."
Microsoft’s action coincides with an ongoing battle between the US tech giant Apple and the Federal Bureau of Investigation (FBI) over whether courts can force cell phone and computer companies to unlock encrypted data on devices needed in criminal investigations.