The Obama administration will argue before a federal appeals court on Tuesday that law enforcement must regain the ability to use GPS tracking devices without a warrant, which it says is necessary to continue the fight against terrorism.

The use of GPS devices in warrantless snooping has been illegal since January 2012, when the Supreme Court ruled that vehicles are private property protected by the Fourth Amendment, which guarantees freedom from unreasonable search and seizure. If the Obama administration is successful on its appeal however, GPS devices will be fair game for police nationwide.

The administration's brief (PDF) in U.S. v. Katzin, filed with the 3rd Circuit Court of Appeals in Philadelphia, goes even further than just arguing for law enforcement's access to the technology: the administration says vehicle tracking is necessary to keep the nation safe from terrorist attacks as well.

Despite the Supreme Court's ruling, the president's attorneys contend the original arguments are invalid because the so-called "automobile exception" to search warrants also applies to data showing where that vehicle is and has been, not just what may be inside.

The brief contends that passing on warrantless GPS tracking when it is a potential investigative tool has a "minimal" effect on safeguarding privacy, but a "great expense" to law enforcement and public safety. "Requiring a warrant and probably cause before officers may attach a GPS device to a vehicle, which is inherently mobile and may no longer be at the location observed when the warrant is obtained, would seriously impede the government's ability to investigate drug trafficking, terrorism, and other crimes."

The brief adds that the legal standard for "slap-on" GPS tracking devices should not be "probable cause" as the Constitution sets out for searches of private property, but "reasonable suspicion," a lesser standard that allows an officer to begin a search for probable cause.

"Just because a technology wasn't around when the Constitution was written doesn't mean that it's not covered," American Civil Liberties Union attorney Catherine Crump said in an advisory. "The fundamental privacy rights established by the Fourth Amendment require that police justify their actions and show probable cause to a judge before they can conduct invasive surveillance like constant location tracking. The 'automobile exception' was created so police could find contraband hidden in cars, not so they could monitor a person's movements nonstop for days or even months on end."