Gathering location data just became trickier for authorities. In a 5-4 decision, the Supreme Court has ruled that accessing a suspect's cell phone location history should require a warrant. The decision came at the end of Carpenter v. United States, the first case about location data the Supreme Court has ruled on.

The case in question started with a robbery in 2011, after which Detroit police acquired 127 days' worth of location data from Timothy Carpenter's cell phone provider. The court's decision says authorities' gathering of Carpenter's location history was a violation of his Fourth Amendment right not to be subject to unreasonable searches and seizures. "The Government's position fails to contend with the seismic shifts in digital technology that made possible the tracking of not only Carpenter's location but also everyone else's, not for a short period but for years and years," Chief Justice John Roberts wrote.

An appeals court had previously ruled that location records are not protected by the Fourth Amendment. Authorities argued that location data is owned by the companies that store it, not the individual that created it, and so it was the prerogative of Carpenter's service provider to hand over the records. In the lead-up to the trial, several major tech companies including Google, Apple, and Facebook had written a letter urging the court to make it more difficult for the government to acquire location history.