Big technology companies have usually played a defensive game with government prosecutors in their legal fight over customer information, fighting or bowing to requests for information one case at a time.

But now, in a move that could broaden the debate over the balance between customer privacy and law enforcement needs, Microsoft is going on the offense.

The software giant is suing the Justice Department, challenging its frequent use of secrecy orders that prevent Microsoft from telling people when the government obtains a warrant to read their emails.

In its suit, filed Thursday morning in Federal District Court in Seattle, Microsoft’s home turf, the company asserts that the gag order statute in the Electronic Communications Privacy Act of 1986 — as employed today by federal prosecutors and the courts — is unconstitutional.