I didn't think Martial law had been declared yet.
As I understand it - I'm no expert - Louisiana does not have a martial law statute, but the declaration of a formal "state of emergency" is pretty much the same thing in that it allows the Governor to do a lot of things she couldn't have without it. Blanco did declare a state of emergency before the storm. Apparently, she didn't use her powers to seize buses in time to be on any help, but is now using it to seize guns.