Except as otherwise provided in this chapter, no person shall be prosecuted under Chapter 7 (§ 18.2-247 et seq.) of Title 18.2 for acting in accordance with § 54.1-3421 or for prescribing, administering, dispensing, or possessing pursuant to a valid prescription issued by a prescriber any substance that has been approved as a prescription drug by the U.S. Food and Drug Administration pursuant to 21 U.S.C. § 360bb and 21 U.S.C. § 355 on or after July 1, 2017, in accordance with any final or interim final order or rule issued pursuant to 21 U.S.C. § 811(j). Such immunity from prosecution for a particular substance shall remain in effect until the earlier of (i) nine months as calculated from the latter of the date of the publication in the Federal Register of the interim final order or rule scheduling such substance or the final order or rule scheduling such substance, provided that a final order or rule is issued within nine months of the interim final order or rule, or (ii) such substance being added to a schedule in Article 5 (§ 54.1-3443 et seq.) pursuant to § 54.1-3443 or by enactment into law.