About the Superdome as a shelter:
It is adjacent to a poorer part of the city, and many of the evacuees show up at the last minute with nothing more than a temper. Second, they opened the 'Dome as a shelter last year diring Ivan, and it was a diasater - fights, vandalism, and general mayhem.
They had reason to resirict items coming in. I have not heard of other shelters making such searches.
.....CLIFF