Singh v. Mukasey, 520 F.3d 119 (2d Cir. Mar. 13, 2008) (Immigration Act of 1990 511(a) five-year 212(c) bar for "an alien who has been convicted of an aggravated felony and has served a term of imprisonment of at least 5 years" held not impermissibly retroactive as applied to one who pled guilty to a disqualifying felony after the Act's enactment, even though he confessed guilt to police prior to the enactment).