Ghanem v. Upchurch, ___ F.3d ___ (5th Cir. March 6, 2007) (DHS decision to revoke a visa pursuant to 8 U.S.C. 1155 is discretionary, and so circuit court has no jurisdiction to review it).
http://caselaw.lp.findlaw.com/data2/circs/5th/0610499cv0p.pdf