The Verge - Google, Microsoft, Yahoo, and Facebook all say that they require full warrants in order to provide the contents of emails and messages to government entities, The Hill reports. That's a higher standard than currently required by US law, which as of now is largely defined by the Electronic Communications Privacy Act (ECPA). The ECPA was passed in 1986 and sets a relatively low bar for accessing private data — but Senator Patrick Leahy has been trying to pass a revision that would require warrants, though the bill stalled out in the last Congress.
While the update for the ECPA is pending, those four companies all gave The Hill variations on the same statement, that they have policies that require a warrant before providing the content of messages. Those policies aren't backed by the force of law yet, however, and there are other reasons for users to still be concerned about how much data government entities can get from these companies without a warrant.