They feel (because they never actually think) that Federal forces are evil and therefore aren't needed. Or at least until they have learned a costly lesson.
The NG is under State direction, not Federal. She can have mutual assistance agreements with other states without the Feds even being involved. The Feds can Federalize the State NG if she ASKS or is in definace of Fed Authority. When Bush went down there, he offered her immediate deployment of reg US Military. She said she "needed 24 hours"to decide, she said THAT in front of Nagin. Don't get sucked in the AP media propaganda nonsense about the NG being under Fed command. They were not. They were, and are, under Blanco's orders. She is still refusing to turn control over NO to the Feds as of right now.
Also, democrats like Blanco don't like to give up control.