I think that was for those who lived in the barracks. Maybe even in military housing. I know I, and two others, took shotguns onto a base without having to even register them with the APs or other other base officials. I think we did mention to the gate guards, which could have been military or police, that we had them in the vehicle.
I only know about the barracks. One of my friends kept my .22 rifle off base in his trailer. The trailer got repossessed after he stopped making payments. I carried him home one night from work and the trailer and all he owned was gone. The telephone was sitting where the trailer had been parked. All he had was the clothes he was wearing. My rifle was gone also. He finally got it back for me. ;0)