The prohibition at certain meetings law ("properly posted") removes the HCP defense from 39-17-1308 (Defenses to unlawful possession of a weapon). However, 39-17-1308(a)(1) would still apply as a defense ("Of an unloaded rifle, shotgun or handgun not concealed on or about the person and the ammunition for the weapon was not in the immediate vicinity of the person or weapon").
Now the confusion would come in the form of the question; Does having the gun in a locked box in your luggage with ammo near it constitute 'concealed on or about your person and the ammunition not in the immediate vicinity of the person or weapon'?
Many times, an LEO, a prosecutor or, (more importantly) a judge must use discretion and look at the intent of the law to determine whether or not a law was broken. Given all the federal laws governing transport of firearms, I'm willing to bet that nobody would ever say anything about a gun that was in your luggage and ready to be lawfully checked for a flight.