United States v. Brignoni-Ponce
United States v. Brignoni-Ponce, 422 U.S. 873 (1975), was a case in which the Supreme Court determined it was a violation of the Fourth Amendment for a roving patrol car to stop a vehicle solely on the basis of the driver appearing to be of Mexican descent.
Source: Wikipedia — United States v. Brignoni-Ponce (CC BY-SA 4.0)