In what must surely be regarded as quite a coup, the Electronic Frontier Foundation has won the support of the inventor of GPS, Roger L Easton, in an attempt to prevent the government using GPS tracking without a warrrant.
Easton was awarded the National Medal of Technology in 2006 after inventing the Timation Satellite Navigation System at the Naval Research Laboratory in the early 1970s.
However, in an amicus brief filed with the Supreme Court on Monday, he and the EFF argue that GPS tracking is fundamentally different from other permitted surveillance technologies - and much more invasive. Using it without a warrant violates Americans' reasonable expectations of privacy, they say.
"This is the first case where the Supreme Court will consider automatic, persistent, passive location tracking by law enforcement," says EFF senior staff attorney Marcia Hofmann.
"The government can use location information over time to learn where you go to church, what sort of doctors you go to, what meetings and activities you participate in, and much more. Police should not have blanket permission to install GPS devices and collect detailed information about people's movements over time without court review."
The case is United States v. Jones, and relates to the fact that FBI agents planted a GPS device on a car while it was on private property. They then used the GPS to track the position of the vehicle every ten seconds for a full month - without obtaining a search warrant.
An appeals court ruled that the surveillance was unconstitutional without a warrant, but the government appealed the decision.
"If police are allowed to plant GPS devices wherever they please, that's essentially blanket permission for widespread, ongoing police surveillance without any court supervision," says EFF legal director Cindy Cohn.
"It's not hard to see how that kind of leeway would be abused. We hope the Supreme Court takes a close look at how this technology works and act to protect the Fourth Amendment rights of Americans."