I think more is needed. The common law authority of posse comitatus (not the act), in which a county Sheriff can “conscript” (armed) citizens “of good character”, “in keeping the peace or to pursue and arrest a felon”, could be of immense value following a disaster.
A Katrina-type hurricane would be a good example. Say a lot of homes had been destroyed or damaged, emergency services do not have free access, there is a strong possibility of looting and robbery, etc.
A deputy would arrive on scene to see a bunch of armed people standing about. He does not see them as a threat, but as an asset. “What are you doing?”, he asks. “Watching over what’s left of our homes”, one of them replies.
“Does anyone have ID that shows you live here?”, and two or three put up their hands, and shows him their ID. “And can you vouch for the other people here?”, and they answer yes.
“Then by the authority of Sheriff... I deputize you all, and will give you a walkie-talkie to communicate with the Sheriff’s office on freq (...) Your instructions are to continue to safeguard your property and the property of your neighbors, and this area will be marked as under your control. Contact the Sheriff’s office to arrange for water, food, temporary shelter, and further instructions.”
Seems like a good idea to me.