the court's ruling in this case rests on the fact that the search at issue in this case took place at the international border. "the government's interest in preventing the entry of unwanted persons and effects is at its zenith at the international border." in light of the government's interest in protecting its sovereignty and territorial integrity, "searches made at the border... are reasonable simply by virtue of the fact that they occur at the border." indeed, the statute authorizing the search in this case derived ultimately from a statute first passed in 1789. smugglers frequently attempt to penetrate the border, and using vehicle gas tanks is a common tactic. 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.