Sen. Patrick Leahy (D-Vt.) is pushing a bill that would require police to obtain a warrant before they seize emails, Facebook messages or other forms of digital communication.
The Senate Judiciary Committee, which Leahy leads as chairman, is scheduled to mark up the legislation this week.
Under the Electronic Communications Privacy Act (ECPA) of 1986, police only need an administrative subpoena, issued without a judge's approval, to read emails more than 180 days old. Police simply swear an email is relevant to an investigation, and then obtain a subpoena to force an Internet company to turn it over.
Civil liberties groups say ECPA is woefully out of date in an era when deleting emails is no longer necessary.
In a blog post, Chris Calabrese, legislative counsel for the American Civil Liberties Union (ACLU), said the policy decisions in 1986 were not "necessarily wrong," but that the result today is an "enormous hole in privacy protections."
Leahy, one of the original co-sponsors of ECPA, said in a statement last year that "updating this law to reflect the realities of our time is essential to ensuring that our federal privacy laws keep pace with new technologies and the new threats to our security.”
Digital Due Process, a coalition of public interest groups and technology companies, has been lobbying Congress to update ECPA. Facebook, Google, Twitter, Apple and AT&T are all members of the coalition.
But Sen. Chuck Grassley (R-Iowa), the Judiciary Committee's top Republican, expressed skepticism about creating new barriers for police investigations.
"I have heard concerns about this amendment from state and local law enforcement officials. These officials are concerned with the impact this amendment may have on law enforcement operations," Grassley said last week. "Specifically, I have heard concerns about how this could impact cases where time is of the essence, namely kidnapping and child abduction cases."
Grassley said he asked for input from the Justice Department, and officials told him the measure could "adversely affect the Department’s activities."
The Obama administration has yet to take a formal position on the bill.
Leahy introduced a bill last year to update ECPA, but it never came up for a vote. His latest attempt at revising the law is to attach his legislation to a separate video privacy bill that has already passed the House.
That bill, which cleared the House last year on a vote of 303 to 116, would update the Video Privacy Protection Act to allow users of Facebook and other social media sites to opt-in to automatically share which online videos they have watched.
The change in the video law is Netflix's top lobbying priority in Washington.
Attaching his privacy protection bill to legislation that lessens regulation might boost Leahy's chances of winning Republican support.