FBI involved in domestic spying?

Laura Rozen asks, “Why were FBI director Mueller and the FBI so involved in Comey’s decision-thinking on the NSA warrantless domestic spying program? Was this about a separate component of the program, that involved the FBI spying without warrants on Americans? Not just the NSA?” And does this explain why Alberto Gonzales claimed in 2006 that the questions of legality raised by Comey were not related to the NSA spying program?

UPDATE: Just out from the Washington Post: the Justice Department responds to the letter about Gonzales’ 2006 testimony we reported on earlier:

The Justice Department said yesterday that it will not retract a sworn statement in 2006 by Attorney General Alberto R. Gonzales that the Terrorist Surveillance Program had aroused no controversy inside the Bush administration, despite congressional testimony Tuesday that senior departmental officials nearly resigned in 2004 to protest such a program.

The department’s affirmation of Gonzales’s remarks raised fresh questions about the nature of the classified dispute, which former U.S. officials say led then-Deputy Attorney General James B. Comey and as many as eight colleagues to discuss resigning.