But lawyers told ABC News that the ruling could have a wide-ranging impact and that it raised a constitutional issue that could eventually find its way to the Supreme Court.
"Whether or not you have a constitutional right of privacy in your stored e-mail has been a dangerously open question over the past 20 years, particularly in recent years when so many of us store all of our personal e-mail with our Web-mail providers," said Kevin Bankston, a staff lawyer with the Electronic Frontier Foundation, which filed a friend of the court brief in the Warshak case.
The Constitution generally grants little protection to personal information that is being held by a third party, such as banks. The conventional wisdom, said Paul Ohm, a University of Colorado Law School professor and former computer crimes prosecutor, was that the same reasoning applied to e-mails.
"E-mail has always been treated as a second-class citizen," he said. "Police were free to engage in more speculative investigations of people's e-mail messages. But [the Sixth Circuit ruling] means that e-mail has been elevated as something that is much more significant and important."
Ohm said he expected lawyers to start raising similar challenges in cases around the country
At the same time, the ruling could make it more difficult for government investigators to gather information on suspected criminals or terrorists, said Kerr.
Investigators would have to gather more incriminating facts about a suspect before they could read personal e-mails.
Kerr also questioned whether the case would be overturned on appeal.
"They were effectively drafting a statute to protect e-mail," he said. "This basically rewrites the law that applies to e-mails."