In Criminal law, Carroll doctrine refers to a principle that permits a police officer to search an entire motor vehicle and any containers inside it if there is probable cause to believe the vehicle contains contraband or the fruits, instrumentalities or evidence of criminal activity. The name comes from the case Carroll v. United States, 267 U.S. 132 (U.S. 1925) a prohibition era case. Carroll created the constitutional difference between searches of dwellings and vehicles.
Carroll doctrine is also used to describe the principle that a broadcast licensee can contest any grant of a competitive license by the Federal Communications Commission on ground that the grant could lead to a diminution in broadcast service by causing economic injury to an existing licensee. The standard was set in Carroll Broadcasting Co. v. Federal Communications Com., 258 F.2d 440 (D.C. Cir. 1958).