The DOT's Office of Drug and Alcohol Policy and Compliance (ODAPC) has released a new official Part 40 Q&A, dated May 2026, that settles a question many carriers and drivers have been asking since marijuana rescheduling took effect last month. The question: can a Medical Review Officer (MRO) verify a lab-confirmed marijuana positive as "negative" if the driver claims the result came from a state-licensed medical marijuana product? ODAPC's answer is an unambiguous no. The guidance, issued jointly by ODAPC and the DOT Office of General Counsel, constitutes official interpretation of 49 CFR Part 40 under 49 CFR § 40.5.
This Q&A is a direct response to confusion generated by the DEA's final rescheduling order, which took effect on April 28, 2026. That order moved certain categories of marijuana from Schedule I to Schedule III of the Controlled Substances Act — specifically, FDA-approved drug products containing marijuana, and marijuana subject to a qualifying state-issued medical marijuana license. As we covered in detail in our April 2026 article on the CDL implications of rescheduling, the change in scheduling status created significant uncertainty among drivers and carriers about what it means for DOT drug testing. This new Q&A speaks directly to that uncertainty, with particular focus on the MRO verification process.
What the ODAPC Q&A Says
The guidance addresses 49 CFR §§ 40.137, 40.141, and 40.151, which are the regulatory provisions that govern how MROs review and verify drug test results. Under 49 CFR § 40.137(a), an MRO must verify a confirmed positive marijuana test result unless the employee presents a "legitimate medical explanation" for the presence of the drug in their system. The central legal question after rescheduling was whether a state-issued medical marijuana card, a physician's recommendation, or dispensary records could now satisfy that standard. ODAPC confirms they cannot.
The Q&A lays out five specific conclusions that carriers, MROs, and drivers need to understand:
There is no scenario in which an MRO can verify a lab-confirmed marijuana positive as "negative" based on a driver's claim that the positive resulted from a state-licensed marijuana product.
Even after rescheduling, state-dispensed marijuana is not an FDA-approved drug. Because it does not have FDA approval, it cannot be prescribed as a controlled substance under federal law.
A "legitimate medical explanation" under Part 40 requires that the employee used a legally prescribed controlled substance in compliance with federal laws governing that prescription. See 49 CFR §§ 40.137(a) and 40.141(b).
Documents presented by an employee, including state-issued medical marijuana cards, physician recommendations or certifications, and dispensary records or receipts, do not satisfy Part 40's requirements for a "legitimate medical explanation."
Marijuana use under state medical marijuana programs or other non-prescription sources does not qualify as a "legitimate medical explanation" under 49 CFR § 40.137(a), and ODAPC restated its longstanding position that marijuana use is not compatible with safety-sensitive functions.
Why This Clarification Was Necessary
The core of the confusion traces back to how Schedule III classification works compared to Schedule I. Substances in Schedule III have an accepted medical use and may lawfully be dispensed by prescription, whereas Schedule I substances cannot. Once state-licensed medical marijuana moved to Schedule III, some drivers and carriers assumed that a physician's recommendation or a dispensary receipt could now serve as the kind of "valid prescription" that an MRO might accept for other controlled substances — the same way a valid opioid prescription can result in a verified negative for an opiate positive. ODAPC's Q&A directly forecloses that argument.
The reason that logic does not hold for marijuana, according to ODAAPC: prescription drugs must receive FDA approval to be dispensed by prescription under federal law. State-licensed marijuana products, regardless of their new Schedule III classification, have not gone through the FDA drug approval process. No physician can write a federally valid prescription for a substance that lacks FDA approval. Without a lawful federal prescription, there is no "legitimate medical explanation" under § 40.137(a), and the existing language of § 40.151 explicitly prohibits MROs from verifying a test negative based on a physician recommendation for a state-authorized substance that is not federally prescribed.
This Q&A also tracks closely with the pre-rescheduling framework that has been in place for years. The DOT's prior guidance on recreational and medical marijuana stated that MROs would not verify a drug test as negative based on information that a physician recommended the employee use "medical marijuana" under state initiatives. The May 2026 Q&A extends and reinforces that position in the post-rescheduling environment, making clear that the reclassification of state-licensed marijuana to Schedule III does not change the MRO's obligations under Part 40.
The Bigger Picture: Testing Authority Under Rescheduling
The MRO question ODAPC addressed in this Q&A is important, but it exists alongside a larger structural question that remains unresolved. As we analyzed in our January 2026 coverage of the marijuana rescheduling executive order, DOT's authority to mandate marijuana testing flows through the Department of Health and Human Services. The HHS Mandatory Guidelines for Federal Workplace Drug Testing Programs authorize regulated employers to test only for drugs listed in Schedule I or II of the Controlled Substances Act. The rescheduling of state-licensed medical marijuana to Schedule III raises a genuine legal question about whether HHS retains statutory authority to include THC in the mandatory federal testing panel for safety-sensitive employees.
ODAPC's May 2026 Q&A does not address that structural testing-authority question. The Q&A is specifically and narrowly focused on the MRO verification process — what an MRO can and cannot accept as a "legitimate medical explanation" once a positive result has already come back from the laboratory. The broader question of whether DOT retains full testing authority over state-licensed marijuana as a Schedule III substance is still pending. The DEA has scheduled an administrative hearing beginning June 29, 2026, which will address the broader rescheduling of all marijuana, and a final outcome of that process could force Congress or HHS to act to preserve the existing testing framework.
For now, the practical answer is unchanged. 49 CFR Part 40 and 49 CFR Part 382 have not been amended. Testing continues under the same rules. A positive marijuana test will result in removal from safety-sensitive duties, mandatory reporting to the FMCSA Drug and Alcohol Clearinghouse, and the driver entering the return-to-duty process. As we detailed in our article on how drivers return to duty following a drug or alcohol violation, that process involves evaluation by a Substance Abuse Professional (SAP), a return-to-duty test, and follow-up testing — and it is not quick or simple for the driver or the carrier managing the program.
What This Means for Your Fleet Right Now
Safety directors need to make sure the message from this Q&A reaches their driver pool clearly and without ambiguity. Many drivers who hold state medical marijuana cards genuinely believe that rescheduling changed their exposure to a positive DOT test. They are wrong, and a positive test will cost them their CDL privileges.
Here is what carriers should do in response to this guidance:
Communicate with your drivers now. Inform them in writing that the ODAPC Q&A confirms no state medical marijuana card, physician recommendation, or dispensary receipt can serve as a legitimate medical explanation for a positive DOT marijuana test. State law is irrelevant to this analysis.
Brief your MRO. If your Medical Review Officer has any questions about how to handle a driver presenting state marijuana documentation during the verification interview, point them directly to the May 2026 ODAPC Q&A and to 49 CFR § 40.137(a). The standard has not changed.
Update your written drug and alcohol policy. If your policy documents reference the Schedule I status of marijuana or reference the pre-rescheduling regulatory framework, update that language to reflect the current environment while making clear that DOT's zero-tolerance position is unchanged.
Confirm your Clearinghouse compliance. A positive test triggers mandatory Clearinghouse reporting obligations. Confirm that your program — whether administered in-house or through a C/TPA — is set up to report violations correctly and that your annual limited query process is current for all existing drivers. Review the FMCSA Clearinghouse for the latest reporting requirements.
Watch the June 29 DEA hearing. The administrative hearing scheduled to begin June 29, 2026 and conclude no later than July 15, 2026 will address the broader marijuana rescheduling proceeding. Trucksafe will cover any developments that affect DOT testing authority and the Part 40 framework.
If you have questions about how your drug and alcohol testing program is structured, whether your written policy reflects current ODAPC guidance, or how to handle a driver who presents marijuana documentation during a test verification, Trucksafe's Compliance+ program provides ongoing regulatory support, document templates, and direct access to compliance resources to help your fleet stay ahead of these developments.
