“Under what authority”
What authority did they need in Katrinafied New Orleans?
There’re problems with such nebulous conditions as “things go(ing) down.” It would take extraordinary circumstances. It could happen, though; maybe not nationally all at once, but here and there incrimentally. It’s happened elsewhere.
Lots of people gave up their weapons during Katrina. I'm sure a few of them were used to posting "from my cold, dead hands!" on internet forums. Yet when the cops pointed their weapons and said "hand 'em over!" they meekly complied.
Whatever authority they thought they had, they didn't have it for long. Insiders voiced enough dissent to shut it down before it got far and public word got around.