For the very small airports, I am told there are police/security employees with basic training in customs procedures.

In general, customs inspections in the EU are very rudimentary. They know that 99% of pax have good intentions, and figure that most of the rest will have been caught by successive rounds of departure security. I think it's accepted that delaying the whole world and his dog in order to occasionally find a little condraband in a suitcase is a pointless excercise when there are miles and miles of land/sea borders that just can't be guarded effectively....

In Mexico and Venezuela (and I think BOG, too, but I 've only flown there once and I can't be totally sure), baggage reclaim is airside and an airline employee carries out a tag inspection on those leaving the belt. Not 100% perfect, but pretty darn close if you ask me.