"We need to keep in perspective ... what was the reality before Sept. 11, what was the law thereafter," Freeh said Tuesday in testimony before the commission.
Freeh said before Sept. 11, 2001, his FBI investigated terror attacks vigorously both in the United States and abroad.
Agents were limited to seeking arrest warrants and building legal cases against suspects, however, Freeh said.
"Absent a declaration of war by the United States against al-Qaida ... we were left with the tools that were available to fight terrorism," Freeh said.
The former director said the FBI never saw its actions as a replacement for military or political actions against al-Qaida, and stressed that the bureau's legal authority and funding restrictions did not allow it to pursue suspects any more fully than it did.
He said funding increases and legal changes including the USA Patriot Act since 2001, have made significant changes to FBI work.