Is privacy dead? If so, someone forgot to tell the Supreme Court. In a ringing unanimous decision Wednesday, the justices said that when police arrest a suspect, they don't have the right to access the data in his cellphone without a search warrant. It's a critical victory for the right of citizens to shield their most private information from government scrutiny.

The verdict was not a foregone conclusion. In recent years, the court has carved out various exceptions to the customary Fourth Amendment requirement that police obtain a warrant before conducting a search. During oral arguments in April, Justice Antonin Scalia suggested that cellphones taken from arrested suspects deserve no special protection. "Our rule has been that if you carry it on your person, you ought to know it is subject to seizure and examination," he said.

But he and his colleagues ultimately rejected the argument that cellphones are indistinguishable from other personal items the cops might examine. "That is like saying a ride on horseback is materially indistinguishable from a flight to the moon," wrote Chief Justice John Roberts. "Modern cellphones, as a category, implicate privacy concerns far beyond those implicated by the search of a cigarette pack, a wallet or a purse."