As best I remember there was some back and forth between the White House, Richard Clarke and Dale Watson (head of the FBI CT Division at the time). The basic story was that everyone was vetted before being given approval to depart. Contrast this kid gloves sort of cursory investigation with the indefinite detention and torture of suspected al Qaeda operatives. What sort of bizarre investigation was actually being conducted in regard to finding 9/11 perpetrators? Advocates of torture buy the notion that the super patriots in the Bush administration were so anxious to protect America from more terrorist attacks that they were willing to push the envelope. This argument doesn't ring true when contrasted with the refusal to properly investigate royal family connections to the attacks. Or when contrasted with the failure of the CIA and FBI to explain why their agents obstructed al Qaeda investigations. Or when the efficacy of the torture program is judged on its stated purpose of getting actionable intelligence. By all appearances the torture program was designed with ulterior intentions. One to taint evidence to avoid civilian courts. Two to attain false information intended to support a foreign policy agenda (i.e. invade Iraq). Three for political advantage--"tough on terror" resonated with much of the public.