Flores-Montano ("Flores") was driving a 1987 Ford Taurus station wagon as he attempted to enter the United States through the port of entry at Otay Mesa, California.

Relying on Ninth Circuit precedent in effect at the time requiring reasonable suspicion for removal of a gas tank, Flores filed a motion to suppress the marijuana found in his car.

In United States v. Montoya de Hernandez, 473 U.S. 531 (1985), the Court had said, "Routine searches of the persons and effects of entrants are not subject to any requirement of reasonable suspicion, probable cause, or warrant."

In the five and a half years preceding the decision in this case, 18,788 drug seizures had occurred at the ports of entry in southern California, and of those involving vehicles, 4,619, or 25%, were from gas tanks.

In addition, instances of persons smuggled in and around gas tank compartments are discovered at the ports of entry of San Ysidro and Otay Mesa about once ever 10 days.