The government has been told that it must have a valid search warrant before seizing and searching emails.
The Sixth Circuit Court of Appeals has ruled that the Fourth Amendment applies to email just as much as to other forms of communication. This guarantees "the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches
and seizures" - unless a warrant has been issued based upon probable cause.
Applying this to electronic communications therefore means that law enforcement bodies can't rely on a court order to force ISPs to give them access to customer emails. Under the Stored Communications Act, it had been deemed legal to do so when the emails were more than 180 days old.
In an ascerbic judgement, the court pointed out that "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 - unless they get a warrant, that is."
It went on to conclude that email communications merited the same status. "Given the fundamental similarities between email and traditional forms of communication, it would defy common sense to afford emails lesser Fourth Amendment protection," it ruled.
The case dated back to 2006, when emails were seized in the trial of Steven Warshak, who was accused of defrauding buyers of his penis enhancement product. Unfortunately for him, his conviction still stands, as law enforcement was deemed to have acted in good faith.
The judgement was welcomed by the Electronic Frontier Foundation, which had filed an amicus brief.
"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," it says.
"We hope that this ruling will spur Congress to update that law as EFF and its partners in the Digital Due Process coalition have urged, so that when the government secretly demands someone's email without probable cause, the email provider can confidently say: "Come back with a warrant."