The case (U.S. v. Warshak) stems back to 2006 when criminal defendant Steven Warshak (the guy behind Enzyte) filed a civil suit against the government for warrantlessly seizing his emails. At the time, the court agreed that Warshak's Fourth Amendment rights had been violated, but that decision was later vacated on procedural grounds.
In 2008, Warshak was found guilty of 93 counts of conspiracy, fraud, and money laundering and received a 25-year prison sentence with a $93,000 fine. He appealed the criminal ruling, thus bringing the Fourth Amendment debate back to court. The Sixth Circuit has again concluded that a warrant is necessary for the government to read your email.
"It would defy common sense to afford emails lesser Fourth Amendment protection," the court said, comparing email to traditional mail and phone calls. "The police may not storm the post office and intercept a letter, and they are likewise forbidden from using the phone system to make a clandestine recording of a telephone call."
The EFF has trumpeted today's ruling as 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."