Perez Pimentel v. Mukasey, 530 F.3d 321 (5th Cir. Jun. 4, 2008) (Attorney General's promulgation of 8 C.F.R. 212.7(d) [the Attorney General generally "will not favorably exercise discretion ... with respect to immigrant aliens who are inadmissible ... in cases involving violent or dangerous crimes, except in extraordinary circumstances, such as those ... cases in which an alien clearly demonstrates that the denial of [relief] would result in exceptional and extremely unusual hardship."] not an ultra vires amendment of 8 U.S.C. 1182(h)(1)(B)), citing Mejia v. Gonzales, 499 F.3d 991, 996 (9th Cir. 2007) (the failure of Congress to provide any standard for the Attorney General's exercise of discretion under 8 U.S.C. 1182(h)(2) meant that Congress has not "directly spoken to the precise question at issue.").