"I drafted this bill with one key principle in mind -- that updates to the Electronic Communication Privacy Act must carefully balance the interests and needs of consumers, law enforcement, and our nation's thriving technology sector," Leahy said.

A group called the Digital Due Process Coalition, made up of tech vendors and privacy groups, since early 2010. The different levels of protection for e-mail and other stored data don't make sense with the growing dependence on cloud computing, the group has argued.

ECPA deals with third-party control of data "imperfectly," with different rules if e-mail is on a suspect's computer, if it's been opened, if it's in transit and if it's stored for 180 days, said James Dempsey, vice president for public policy at the Center for Democracy and Technology.

"You have this mishmash of rules, and yet, it's the same content, and we all treat it as if it were the same," he said at a Tuesday debate on ECPA reform at the Brookings Institute. "Increasingly, it sits in a place where ECPA says it's unprotected."

Federal law enforcement agencies have questioned the need for an ECPA overhaul. There's a long legal history of information given to a third party not being protected with a search warrant standard, said Valerie Caproni, general counsel of the U.S. Federal Bureau of Investigation.