Under the Emergency Management Assistance Compact, which was revised after 9/11, the Federal Government and FEMA are not allowed to interfere with local operations unless they are authorized by state and local leaders.
Meanwhile Blanco had her own advisors insisting that the President was actually making a request for federal takeover of the Louisiana National Guard, and asking to put Louisiana State Police under federal control. They were concerned that this would be the same as martial law and lead to abuse of power by the federal government.
By Tuesday, August 30, the federal relief effort began shipping food, water and medical supplies toward Louisiana for use in New Orleans. The same operation was underway in Mississippi and Alabama. The governors of those states had a already signed on to federal help and relief was pouring in. Governor Blanco was the lone holdout. She had still not made a decision.
The Department of Defense sent search and rescue experts, doctors, nurses and support personnel. FEMA was there to help as much as they could but local and state officials would not allow them to participate because Governor Blanco still had not given her permission.
On Thursday, September 1, amid a growing clamor of questions about the lack of action being taken in New Orleans, Blanco finally signed Executive Order KBB-2005-23, giving permission for the federal government to enter Louisiana with military assistance. FEMA began to move supplies into the stricken parishes along the path of Katrina. The Red Cross was finally given permission to deliver the food and water it had stockpiled in the area.
http://www.northsidejournal.com/special2.htm