"Moving marijuana from Schedule I to Schedule III, without other legal changes, would not bring the state-legal medical or recreational marijuana industry into compliance with federal controlled substances law. With respect to medical marijuana, a key difference between placement in Schedule I and Schedule III is that substances in Schedule III have an accepted medical use and may lawfully be dispensed by prescription, while Substances in Schedule I cannot. However, prescription drugs must be approved by the Food and Drug Administration (FDA). Although FDA has approved some drugs derived from or related to cannabis, marijuana itself is not an FDA-approved drug. Moreover, if one or more marijuana products obtained FDA approval, manufacturers and distributors would need to register with DEA and comply with regulatory requirements that apply to Schedule III substances in order to handle those products. Users of medical marijuana would need to obtain valid prescriptions for the substance from medical providers, subject to federal legal requirements that differ from existing state regulatory requirements for medical marijuana. 

"Rescheduling marijuana would not affect the medical marijuana appropriations rider. Thus, so long as the current rider remains in effect, participants in the state-legal medical marijuana industry who comply with state law would be shielded from federal prosecution. If the rider were to lapse or be repealed, these persons would again be subject to prosecution at the discretion of DOJ. 

"With respect to the manufacture, distribution, and possession of recreational marijuana, if marijuana were moved to Schedule III, such activities would remain illegal under federal law and potentially subject to federal prosecution regardless of their status under state law. 

"Some criminal penalties for CSA violations depend on the schedule in which a substance is classified. If marijuana were moved to Schedule III, applicable penalties for some offenses would be reduced. However, CSA penalties that apply to activities involving marijuana specifically, such as the quantity-based mandatory minimum sentences discussed above, would not change as a result of rescheduling. DEA is not required to set annual production quotas for Schedule III controlled substances. 

"The prohibition on business deductions in Section 280E of the Internal Revenue Code applies to any trade or business that “consists of trafficking in controlled substances (within the meaning of schedule I and II of the Controlled Substances Act) which is prohibited by Federal law or the law of any State in which such trade or business is conducted.” Because the provision applies only to activities involving substances in Schedule I or II, moving marijuana from Schedule I to Schedule III would allow marijuana businesses to deduct business expenses on federal tax filings. Other collateral legal consequences would continue to attach to unauthorized marijuana-related activities."

Source

Joanna R. Lampe, Legislative Attorney. Legal Consequences of Rescheduling Marijuana. LSB11105. Congressional Research Service. January 16, 2024.