United States v. Norbury, 492 F.3d 1012, ___ (9th Cir. Jun. 25, 2007) (determination of whether current controlled substances offense was committed after a prior conviction for a felony drug offense has become final, so as to enhance federal sentence under 21 U.S.C. 841(b)(1)((A)-(D) is made under federal law, not state law; under federal law: "An expunged or dismissed state conviction qualifies as a prior conviction if the expungement or dismissal does not alter the legality of the conviction or does not represent that the defendant was actually innocent of the crime."), following Dickerson v. New Banner Inst., Inc., 460 U.S. 103, 115, 103 S.Ct. 986, 74 L.Ed.2d 845 (1983).