Except as otherwise provided in this chapter, a substance the manufacture, distribution, dispensing, or possession of which is explicitly exempt from criminal penalty under federal law is exempt from the application of this chapter and AS 17.30. This exemption includes any substances that may, under 21 U.S.C. 301-392 (Food, Drug, and Cosmetic Act), be lawfully sold over the counter without a prescription. This exemption also includes those substances listed in 21 C.F.R. Sec. 1308.22 on April 1, 1980.