"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.
At the international border, where national security and territorial integrity are paramount concerns for the government, searches made at this location are deemed acceptable solely because of their location, reflecting a long-standing legislative tradition dating back to 1789.