Well here is the rest of that statement.

"We recommend that you provide the key or combination to the security officer if he or she needs to open the container. You should remain in the area designated by the aircraft operator or TSA representative to take the key back after the container is cleared for transportation. If you are not present and the security officer must open the container, we or the airline will make a reasonable attempt to contact you. If we can't contact you, the container will not be placed on the plane. Federal regulations prohibit unlocked gun cases (or cases with broken locks) on aircraft."

Bolding mine