Lee argued that people use their email accounts as "digital filing cabinets," and that digital records should receive the same privacy protections as physical records.
Traditionally, the courts have ruled that people have limited privacy rights over information they share with third-parties. Some police have argued that this means they only need a subpoena to compel email providers, Internet service companies and others to turn over their customers' sensitive content.
Leahy pushed similar legislation at the end of last Congress. His Judiciary Committee approved the bill, but it never reached the floor for a vote.
Reps. Zoe Lofgren (D-Calif.), Ted Poe (R-Texas) and Suzan DelBene (D-Wash.) have introduced legislation in the House that would require a warrant to access mobile location data in addition to emails and other online messages.
The Senate bill introduced on Tuesday, the Electronic Communications Privacy Act Amendments Act of 2013, would require the government to promptly notify someone if their private online information has been accessed. The government can obtain a court order to delay notification to protect an ongoing investigation.
There was broad consensus among lawmakers and law enforcement officials for expanding ECPA at a House Judiciary Committee hearing on Tuesday morning.
The Justice Department's Elana Tyrangiel agreed that police should need a warrant for email searches in criminal investigations, but she urged lawmakers to exempt civil regulators.
Leahy's bill would not exempt civil investigations, covering issues such as antitrust, financial and environmental rules, from the warrant requirement, although it would clarify that regulators can serve subpoenas directly to companies for their records.
Privacy advocates, including the American Civil Liberties Union and the Center for Democracy & Technology, applauded Leahy and Lee for introducing the legislation.
“Our emails contain the most intimate details of our lives and therefore deserve the full protections of the Fourth Amendment,” Chris Calabrese, a legislative counsel for the ACLU, said.