Whether the Fourth Amendment permits Border Patrol roving patrols near the Mexican border to stop vehicles for immigration questioning without individualized reasonable suspicion.
Holding
No. Away from the border and its functional equivalents, a Border Patrol roving patrol may stop a vehicle only when specific, articulable facts and rational inferences from them reasonably suggest that the vehicle contains persons who are unlawfully present in the United States.
Reasoning
A vehicle stop, even when brief and limited to questioning, restrains the occupants' freedom to leave and is therefore a Fourth Amendment seizure. Its legality turns on reasonableness, which requires balancing the Government's substantial interest in enforcing immigration law against the individual's interest in freedom from arbitrary official interference.
The Government had a powerful interest in detecting unlawful entry and preventing the inland transportation of undocumented immigrants. The Court also recognized that a roving-patrol stop is less intrusive than an arrest or a vehicle search: it usually involves a short delay, a few questions, and perhaps a request for documents. Those considerations justified a standard lower than probable cause.
Drawing on Terry v. Ohio and Adams v. Williams, the Court held that officers may make a limited investigative stop on reasonable suspicion rather than probable cause. In the border-enforcement context, that means officers must be able to identify particular facts that reasonably indicate a vehicle may be transporting people unlawfully present in the country.
The immigration statutes on which the Government relied did not eliminate the Fourth Amendment's requirements. Congress may authorize immigration officers to interrogate or search in specified circumstances, but no statute can authorize conduct that the Constitution forbids.
Permitting suspicionless roving-patrol stops throughout the border region would give officers virtually unbounded discretion over lawful motorists. Because the governing regulation defined the relevant border area as within 100 air miles of the border, the Government's position would have permitted random stops across a vast area containing major cities and large volumes of ordinary traffic. The Court found that intrusion unnecessary because alien-smuggling activity commonly produces particularized, observable grounds for suspicion.