The decision (.pdf) in what is arguably the biggest Fourth Amendment case in the computer age, rejected the Obama administration’s position that attaching a GPS device to a vehicle was not a search. The government had told the high court that it could even affix GPS devices on the vehicles of all members of the Supreme Court, without a warrant.

“We hold that the government’s installation of a GPS device on a target’s vehicle, and its use of that device to monitor the vehicle’s movements, constitutes a ‘search,’” Justice Antonin Scalia wrote, declining to say whether that search required a warrant.