The Supreme Court tells law enforcement that if you want to slip a tracking device on a suspect's car, you had better get a warrant first.

FOX News Radio White House correspondent Mike Majchrowitz reports from Washington:

It's a case of new technology running up against old Constitutional protections. A unanimous Supreme Court ruling police do need a warrant before they can plant a GPS tracker on a suspect's car.

Law enforcement thought that since they were tracking this drug suspect on public streets, his rights to privacy were not infringed upon. They had a warrant, but not one that covered the tracking device.

Justice Antonin Scalia wrote "officers encroached on a protected area" by attaching that GPS device, specifically an area protected by the Fourth Amendment's limits on search and seizure.

In Washington, Mike Majchrowitz, FOX News Radio