The Electronic Frontier Foundation (EFF) has submitted a friend-of-the-court brief [PDF] in a case that could have a profound effect on the privacy of Internet communications.

The brief argues that the decision in US v. Councilman, soon to be reheard by the full First Circuit, should be overturned. A panel of First Circuit judges previously ruled that it does not violate criminal wiretap laws when an email service provider monitors the content of users’ incoming messages without their knowledge or consent.

The defendant in the case, Bradford Councilman, is a bookseller who offered email service to his customers. Councilman configured the email processing software so that all incoming email sent to his customers from Amazon.com, a competitor, was secretly copied and sent to his personal email account before it arrived in the intended recipient’s mailbox. The court ruled that this interception did not violate federal law, stating that “it may well be that the protections of the Wiretap Act have been eviscerated as technology advances.”

Authored by law professor and online privacy expert Orin Kerr, the amicus brief is co-signed by EFF, the Center for Democracy and Technology (CDT), the Electronic Privacy Information Center (EPIC), the American Library Association (ALA), the American Civil Liberties Union (ACLU), and the Center for National Security Studies. These groups argue that the earlier Councilman decision disrupts the traditional understanding of Internet surveillance laws and raises significant constitutional questions under the Fourth Amendment.

“The First Circuit’s original decision effectively rewrote the field of Internet surveillance law in ways that Congress never intended,” said Kevin Bankston, EFF attorney and Equal Justice Works/Bruce J. Ennis fellow. “If private service providers like Councilman can avoid the Wiretap Act’s criminal prohibition on interception, it follows that the government will also be able to monitor our communications without having to ask a judge for a wiretap order. If the decision is allowed to stand, it will eliminate the Wiretap Act as the primary curb against private and government snooping on the Internet.”

The original panel decision has been withdrawn pending the First Circuit’s rehearing of the case, which will take place in December.