And just to add to that:

I scenarioed a Katrina type disaster sometime ago. With large numbers of people under canvas. For months with inadequate numbers of LEO's.

You need armed citizen's either deputised or as posse comatus. To maintain rule of law. That means dealing with the predators. Muggers, Thieves, Wannanbe rapists etc.

No, the no weapons rules may not always be a good idea.