That's true at the local level. But under the Texas Government Code, Section 418, once the Governor declares a "state of disaster" he can, according to 418.019, "suspend or limit the sale, dispensing, or transportation of alcoholic beverages, firearms, explosives and combustibles." So have plenty of ammo on hand.
It should be noted that Governor Perry has never ventured onto this particular political landmine.

I will say, from my experience, the current climate supports CHL holders even during a state of disaster. After the Katrina debacle when lawfully owned firearms were seized, no elected official really wants to step into that again.
I'm sure Charles has more that he can add to this.
T.