Signage carry's the weight of the law. Despite the fact there is no regulation on how the sign just be displayed, size, location or contents.
Folks who have never experienced this can't begin to appreciate how bad it is.
I worked in downtown Charlotte for a about 3 years, about the same as DT Atlanta.
Skyscrapers about the same.
The building owner could put one decal on one pane of glass on the ground floor, no background, regular 12 point type, and that made it illegal to carry a weapon anywhere in the 40 story building. They don't have to (or at least don't) have to put the notice at every entrance.