The moment looting started, the Governette (no insult intended to women in general, intending to designate her as a lightweight) should have declared a State of Insurrection - it's not a mark of shame, just a statement of fact. At that point, the looters would have been crushed by the elements of the 82nd Airborne and 2nd Marine Division that are *ON THE GROUND NOW* and that would have been the end of it.
Since she still hasn't done that, they can only use National Guard units for patrols and such. The regular military and reserve is restricted to humanitarian and rescue operations only. They can shoot back, but only in self-defense and only in more extreme cases. The only other way they can get involved (other than if dumbsh** gets off her liberal butt and makes the declaration) is if Congress passes an act authorizing it. That would, naturally, take weeks.
What worked then should work now. It is past time to hide under the covers of "the rule of law" and "states' rights", much less the phrase, "help is coming real soon". The looters and snipers must be suppressed without mercy, and the remaining population of New Orleans must be entirely and quickly evacuated under the strict supervision of the regular military and Federalized National Guard.