Even your link does not support your assertion. It is a classic example of quote mining. The full quote seems to be...
WASHINGTON D.C. -- Michael D. Brown, Under Secretary of Homeland Security for Emergency Preparedness and Response and head of the Federal Emergency Management Agency (FEMA), today urged all fire and emergency services departments not to respond to counties and states affected by Hurricane Katrina
without being requested and lawfully dispatched by state and local authorities under mutual aid agreements and the Emergency Management Assistance Compact.
“The response to Hurricane Katrina must be well coordinated between federal, state and local officials to most effectively protect life and property,” Brown said. “We appreciate the willingness and generosity of our Nation’s first responders to deploy during disasters. But such efforts must be coordinated so that fire-rescue efforts are the most effective possible.”
I have highlighted the part you left out that changes the intent and meaning of the FEMA release.
In addition, the release was from the 29th. and so very early in the incident.
I think it would be good if you go back and edit a notice into your post clarifying what was really said.