Is the term 'controlled substance' in § 4B1.2(b) limited to those substances defined and regulated under the federal Controlled Substances Act, 21 U.S.C. § 801 et seq.?

QUESTION PRESENTED The Federal Sentencing Guidelines provide for an enhanced advisory Guideline range for certain offenses if the defendant has a prior conviction for a “controlled substance offense,” as that phrase is defined in USSG § 4B1.2(b). The question presented is: Is the term “controlled substance” in § 4B1.2(b) limited to those substances defined and regulated under the federal Controlled Substances Act, 21 U.S.C. § 801 et seq.? i