Ebrahim v. Gonzales, 471 F.3d 880 (8th Cir. Dec. 22, 2006) (court of appeal lacked jurisdiction to review petition for review of waiver denial under 8 U.S.C. 1186a(c)(4), because question whether a marriage has been entered into in "good faith" is a matter within the unreviewable discretion of the Attorney General).
http://caselaw.lp.findlaw.com/data2/circs/8th/054433p.pdf