When you arrive at ATL (unless this has been changed recently) on an international flight you have to go through Security even if you have no connecting flight.

The reason is that after going through Customs you have to enter the secure area of the airport before leaving the airport itself.

This could lead to the absurd situation where somebody legally gets on a flight in France with a Bic and gets arrested in Atlanta for trying to take a cigarette lighter out of the airport!