FISC/FISA is clearly not working as a procedure for keeping the NSA in check. Why? Because "secret accountability" is a contradiction in terms. It isn't real accountability, it's conspiracy, because the wall of secrecy is drawn around the two of you, and all information is forbidden from leaving, ever.
Mokalus of Borg
PS - Self-policing always devolves into no policing.
PPS - Because it's easier that way.