Carpenter v. United States

Police generally need a warrant to get your cell phone location history from your carrier. The government cannot simply subpoena your phone company for months of location data without going through a judge.

Government access to cell-site location information (CSLI) — historical cell phone location records — constitutes a Fourth Amendment search requiring a warrant.

Landmark digital privacy case. Protects cell phone location data. Extended Fourth Amendment protection to digital records in the hands of third parties.