My take on the situation: One problem, the national guard was in Iraq, not Louisiana like it should have been. Another problem is that providing assistance to people in need does not violate Posse Comitatus, and once the national guard is called in the area is placed under martial law, habeas corpus is suspended and Posse Comitatus at that point does not apply.
Krugman had the most damning assessment from a post he wrote at the time:
Even military resources in the right place weren’t ordered into action. “On Wednesday,” said an editorial in The Sun Herald in Biloxi, Miss., “reporters listening to horrific stories of death and survival at the Biloxi Junior High School shelter looked north across Irish Hill Road and saw Air Force personnel playing basketball and performing calisthenics. Playing basketball and performing calisthenics!”
There's only one thing I can say about Rummy, this was UNCONSCIONABLE!