[Lunatic Fringe]

Look- the Secret Service is the only federal agency in the Executive Branch that can give the President an order. They believed his life may have been in danger, and the safest place for him was on Air Force One.

When the President's life is in danger, the Secret Service is obligated to protect him. Even if he ORDERED AF1 to fly to Washington, the Secret Service would have said "No way."

[Paul Atreides]

If W had gone back to D.C. right away, he would have been branded a wreckless cowboy, trying to look like John Wayne.

[Timesink]

Look- the Secret Service is the only federal agency in the Executive Branch that can give the President an order. They believed his life may have been in danger, and the safest place for him was on Air Force One.

While it's quite rare for a President to go against the recommendations of the Secret Service (and Bush obviously did not on 9/11), I don't think a President is legally bound to follow their orders.