This is about The F.I.S.A Bill that expired over the weekend.?

IF letting this bill expire will jepardize national security enormousy than why Did Bush refuse to sign it if it didnt include immunity for the telecoms? Is he saying that if we dont give these phone companies a get out of jail free card than he will jepardize our national security? thats what it sounds like to me. and if tapping the phones of americans helps us fight terrorism than what happend on 9/11 we know he was wire tapping before 9/11 so why through his wire tapping wasnt that prevented?