The Sixth Court of Appeals handed down an important decision today, ruling that police must obtain a search warrant before going through emails stored by an Internet Service Provider. The case, United States v Warshak, is the first in which the court specifically addresses the question of whether or not the Fourth Amendment applies to email communications.

The case did affirm the fraud conviction of Steven Warshak, whose emails were read without a warrant. Nevertheless in its decision, the court challenged part of the Stored Communications Act - the law that, up 'til now, has afforded the government warrantless search access in certain cases.

The Stored Communications Act (SCA) was passed in 1986 - "eons ago" in terms of the development of Internet technologies and our increasing reliance on email as a form of communication. The act, in part, prohibits ISPs from divulging email messages to anyone other than the intended recipients. But the law also addresses the circumstances in which the government would not be required to get a warrant to search messages - such as for messages over 180 day old. The weaker protections for email under the Fourth Amendment have been a contentious issue for a long time, but no clear court decision has come down, until today.

In making its decision, the court recognized how technology and communication had changed: "Since the advent of email, the telephone call and the letter have waned in importance, and an explosion of Internet-based communication has taken place," the 3-1 decision reads. "People are now able to send sensitive and intimate information, instantaneously, to friends, family, and colleagues half a world away. Lovers exchange sweet nothings, and businessmen swap ambitious plans, all with the click of a mouse button."

As a result, the Court of Appeals says that "It follows that email requires strong protection under the Fourth Amendment; otherwise, the Fourth Amendment would prove an ineffective guardian of private communication, an essential purpose it has long been recognized to serve." The EFF, which had filed an amicus brief, hailed today's ruling as a "landmark decision."