Tough to stop people from shitting where they eat. They could but they would need enough bodies to sweep through and announce curfew. Nixon does not have the balls for that.
Looters and arsonists should be shot on sight. If police want to defuse this by standing by, at least they could bring lots of lights and cameras to identify people for later prosecution. Otherwise, as we seem to be seeing, rioters, looters, and arsonists are loose animals with no apparent care about the consequences of their violence.