...that when this country was first founded international travel was expensive and rare. It mostly occured for the purposes of commercial shipping. Neighboring Canada and Mexico were actively hostile countries. The things searched for at these borders were likely limited in scope to commercial tarrif enforcement and possibly espionage. A great deal has changed in 200 years. Neighboring Canada and Mexico are no longer enemies. The cost and time involved in international travel has plummeted, and the amount of travel has exploded. Furthermore, the things searched for have expanded far beyond enforcement of commerical tarrifs to include personal contraban of various sorts, personal import limits, intellectual property crimes, and anti-terrorism. Essentially, the number of people travelling has gone way up and the intrusivness of searches has gone way up, and so the psychological impact of these searches has increased. What before might have seemed reasonable now feels very much like the actions of a police state, and may no longer be Constitutionally sound (in fact if not as a matter of law).