As Reason.com reports, in a recent case in federal court in northern California,
Officials sought the right to track suspects' Cell Site Location Information, or CSLI, for 60 days without gaining a warrant. Such location information lets law enforcement track the whereabouts of our cell phones in relation to cell towers. . . .
The government argued the public can avoid their surveillance by not using a cell phone. But [Judge Lucy] Koh rejected that argument: "Considering the ubiquity of cell phones, and the important role they play in today's world, it is untenable to force individuals to disconnect from society just so they can avoid having their movements subsequently tracked by the government."
She ruled that the government needs a warrant — and not just a court approval, which is based on lower standards of proof. Warrants require probable cause.
Read the story here.