Cannabis Drug Testing Carve-Out: Harris-Sessions Bill Targets Transportation Workers After Schedule III

The federal cannabis rescheduling debate has a new flashpoint, and it has nothing to do with whether marijuana will move to Schedule III. It has to do with what happens to the millions of safety-sensitive transportation workers — commercial truck drivers, airline pilots, railroad operators, transit drivers, and merchant mariners — once it does.

Reps. Andy Harris (R-MD) and Pete Sessions (R-TX) have joined with an anti-marijuana coalition and a drug-testing industry association to push for a "safety carve-out" that would preserve federal drug-testing authority for cannabis even after the Drug Enforcement Administration completes its expected reclassification from Schedule I to Schedule III. The proposal is small in legislative footprint but big in consequence: it would lock cannabis into the U.S. Department of Transportation's Part 40 testing program no matter what the DEA decides at its June 29, 2026 rescheduling hearing.

What the Harris-Sessions Carve-Out Actually Does

The proposed language would explicitly maintain marijuana on the DOT's prohibited substances list and continue to require pre-employment, post-accident, random, reasonable-suspicion, and return-to-duty testing for THC in any worker covered by 49 CFR Part 40. That includes commercial driver's license holders, pilots and crew, transit and intercity bus operators, hazmat handlers, certain pipeline workers, and Coast Guard–regulated mariners.

In practice, the carve-out would create a clean exception to anything the rescheduling order might otherwise do to federal employment policy. Even if cannabis becomes a Schedule III drug — putting it in the same federal category as ketamine, codeine combinations, and anabolic steroids — DOT-regulated workers would still face the same zero-tolerance standard they face today. The drug panel would not change, the urine-screen cutoff for THC metabolites would stay at 50 ng/mL (with a 15 ng/mL confirmation), and a positive result would still trigger the standard removal-from-duty and substance-abuse-professional process.

The proposal is being championed by Smart Approaches to Marijuana (SAM), one of the most active organizations opposing federal rescheduling, alongside the Drug & Alcohol Testing Industry Association (DATIA). Both groups argue that without a carve-out, the rescheduling could erode the legal basis for testing safety-sensitive workers and increase the risk of impaired operation in industries with catastrophic consequences for failure.

Why Transportation Worker Testing Is Already in the News

The carve-out push lands in the middle of a real and measurable shift in cannabis-related drug-test results for transportation workers. According to Federal Motor Carrier Safety Administration data published in the FMCSA Clearinghouse, marijuana has been the most frequently identified substance in commercial driver positive tests every year since the database launched in 2020, regularly accounting for more than half of all positive results among interstate truck drivers. Total positive drug tests in the Clearinghouse have hovered above 200,000 in each of the last several years, with cannabis representing the largest single category.

Carriers and unions have been split on what to do about it. Some operators argue that pre-employment and random testing rules out qualified drivers in legal-cannabis states for use that happened days or weeks before duty, when impairment is no longer present. Others — particularly insurers and large fleets — insist that the existing rules are the floor, not the ceiling, and that any softening of marijuana testing would raise crash exposure and premiums.

The Harris-Sessions language is designed to settle that fight in favor of the existing framework before rescheduling can disturb it.

What Rescheduling Would and Would Not Change on Its Own

Even without the carve-out, federal rescheduling does not automatically end workplace drug testing for cannabis. Schedule III status would acknowledge that marijuana has accepted medical use and a lower abuse potential than Schedule I drugs like heroin or LSD, but Schedule III substances are still controlled substances under the Controlled Substances Act. They are tested for in many federal contexts and remain prohibited without a valid prescription.

The DOT's testing authority comes from the Omnibus Transportation Employee Testing Act of 1991, which directs the Secretary of Transportation to require testing for "controlled substances" — a list that the DOT has historically managed by reference to the DEA's schedules. Schedule III placement, on its own, does not remove marijuana from that list. What it could do is open new procedural questions: whether a state-issued medical marijuana recommendation could function as a defense, whether the Medical Review Officer (MRO) process needs updating, and whether the Substance Abuse and Mental Health Services Administration (SAMHSA) urine-testing guidelines need to be revised.

The Harris-Sessions carve-out is designed to short-circuit all of those questions and explicitly affirm — by statute — that marijuana stays in the DOT panel, full stop.

The Coalition Pushing Back

Cannabis reform organizations have responded sharply. NORML, the Marijuana Policy Project (MPP), and Americans for Safe Access all argue that singling out cannabis for special workplace treatment after a federal acknowledgment of medical value undermines the whole point of rescheduling. They also point out a long-standing technical problem with cannabis workplace testing: standard urine panels detect non-impairing THC metabolites that can persist for weeks after use, making positive results a poor proxy for actual impairment on duty.

Several major unions — including the Teamsters and segments of the rail and transit labor coalitions — have signaled openness to revisiting cannabis testing, particularly for back-office and non-safety-sensitive personnel. They have generally been reluctant to support broader changes to safety-sensitive testing without a validated impairment-based alternative, but they have also resisted being legislatively locked into the current regime.

Where This Goes Next

The carve-out has not yet been introduced as standalone legislation. Insiders expect it to surface as a rider attached to a larger transportation or appropriations vehicle in the second half of 2026, after the DEA's expedited rescheduling hearing concludes on or before July 15. That timing is deliberate: if Schedule III placement clears the hearing, the carve-out lets its sponsors say they are merely preserving the status quo for transportation safety, not opposing federal reform itself.

For employers, fleets, and safety-sensitive workers, the practical guidance has not changed. DOT-regulated cannabis testing rules remain fully in effect. State-issued medical marijuana cards are not a defense to a federal positive. And nothing about the rescheduling order issued in April 2026 has altered the testing panel.

What is changing is the politics. The next phase of the rescheduling debate is no longer about whether cannabis is medicine. It is about which federal systems will recognize the change and which will be carved out by statute regardless.

Key Takeaways

• Reps. Andy Harris (R-MD) and Pete Sessions (R-TX) are pushing a "safety carve-out" to keep marijuana on the DOT drug-testing panel even after federal Schedule III placement.
• The carve-out would preserve pre-employment, random, post-accident, reasonable-suspicion, and return-to-duty cannabis testing for all 49 CFR Part 40 workers.
• Cannabis has been the single most common positive substance in the FMCSA Clearinghouse for commercial drivers every year since 2020.
• Schedule III placement on its own does not end DOT cannabis testing; the legal framework still treats marijuana as a controlled substance.
• The proposal is expected to appear as a rider on a larger transportation or appropriations bill after the DEA's June 29 rescheduling hearing concludes.

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