A ruling by the Sixth Circuit Court of Appeals has determined that the government has to have a search warrant before it can secretly seize and search emails stored by service providers, and that email privacy is protected by the fourth amendment. 

The ruling came in an appeal of Warshak v. United States, a case which is described by the EFF in the following manner:

EFF and other civil liberties groups filed an amicus brief in Warshak v. United States urging the 6th U.S. Circuit Court of Appeals to hold that the government’s seizure of email without a warrant violated the Fourth Amendment and federal privacy statutes, as well as the Justice Department’s own surveillance manual.

During its criminal investigation, the Department of Justice illegally ordered defendant Stephen Warshak’s email provider to prospectively "preserve" copies of his future emails, which the government later obtained using a subpoena and a non-probable cause court order. The government accomplished this "back door wiretap" by misusing the Stored Communications Act (SCA), which is only supposed to be used for obtaining emails already in storage with a provider.

According to the EFF, the ruling finds that email users have the same reasonable expectation of privacy in email as with phone calls and postal mail. 

"Today’s decision is the only federal appellate decision currently on the books that squarely rules on this critically important privacy issue, an issue made all the more important by the fact that current federal law–in particular, the Stored Communications Act–allows the government to secretly obtain emails without a warrant in many situations," said EFF Senior Staff Attorney Kevin Bankston.

Bankston added that the EFF hopes the decision will "spur congress" to update the law.