For the first time, a federal appeals court has ruled that law enforcement must obtain a warrant to get people’s phone location histories from their cell service companies.

“The court’s opinion is a resounding defense of the Fourth Amendment’s continuing vitality in the digital age,” said American Civil Liberties Union Staff Attorney Nathan Freed Wessler, who argued the case before the 11th Circuit Appeals Court as a friend-of-the-court in April. “This opinion puts police on notice that when they want to enlist people’s cell phones as tracking devices, they must get a warrant from a judge based on probable cause. The court soundly repudiates the government’s argument that by merely using a cell phone, people somehow surrender their privacy rights.”