Microsoft has sued the U.S. government for the right to tell its customers when a federal agency is looking at their emails. The lawsuit, filed on Wednesday in federal court in the Western District of Washington, argues that the U.S. government is violating the U.S. Constitution by preventing Microsoft from notifying customers about government requests for their emails and other documents.

Microsoft says over the past 18 months it has received 5,624 legal orders under the ECPA, of which 2,576 prevented Microsoft from disclosing that the government is seeking customer data through warrants, subpoenas and other requests. Most of the ECPA requests apply to individuals, not companies, and provide no fixed end date to the secrecy provision, Microsoft said.

The government’s actions contravene the Fourth Amendment, which establishes the right for people and businesses to know if the government searches or seizes their property, the suit argues, and the First Amendment right to free speech.

Using the outdeted Electronic Communications Privacy Act, the government is increasingly directing investigations at the parties that store data in the cloud, Microsoft says.

The lawsuit represents the newest front in the battle between technology companies and the U.S. government over government surveillance.