The U.S. Supreme Court has been asked to address whether federal drug law that criminalizes possession of marijuana invalidates state orders requiring employers and their workers compensation insurers to pay for medical marijuana prescriptions for employees injured on the job.

However, before it fully takes on the question, the high court has asked the Solicitor General, who represents the federal government before the high court, for guidance in light of the Supremacy Clause of the U.S. Constitution that gives federal statutes primacy over state laws.

Five state supreme courts have addressed whether the reimbursement of medical marijuana costs is permissible, with two ruling yes and three ruling no. The Supreme Court is being asked to resolve this split in authority.

Under the federal Controlled Substances Act (CSA), the manufacture, distribution or possession of marijuana is a criminal offense, with the exception of when the drug is part of a Food and Drug Administration research study.

The Supreme Court’s involvement is related to two cases from Minnesota—Bierbach v Diggers Polaris and State Auto/ United Fire & Casualty and Musta v. Mendota Heights Dental Center and Hartford Insurance Group—in which injured employees challenged their employers and their insurers for refusing to reimburse them for their medical marijuana prescriptions. Musta suffered a neck injury in her work at a medical facility, while Bierbach was injured in an accident while working for an all-terrain vehicle dealer.

Minnesota authorized the use of marijuana for medical purposes in 2014. Under the state’s medical marijuana act, the Minnesota Department of Health administers a program that permits certain registered patients to possess marijuana for medical purposes.

Under Minnesota’s workers compensation statute, if an employee sustains an injury at work, “[t]he employer shall furnish any medical…treatment, including…medicines…as may reasonably be required at the time of the injury and any time thereafter to cure and relieve from the effects of the injury.”

Minnesota’s Workers’ Compensation Appeals Court ruled in Bierbach’s favor that the employer and insurer were required to reimburse him because the prescribed medical marijuana was a reasonable treatment for the worker’s injuries.

But the insurer and employer appealed, and a divided Minnesota Supreme Court ruled the opposite, finding that the CSA preempts the Minnesota workers compensation court’s order mandating reimbursement.

Minnesota’s high court adopted the same reasoning in both the Bierbach and Musta opinions, finding that the reimbursement could expose the employer and insurer to criminal liability. Specifically, the court reasoned that the CSA preempted an order “obligat[ing] an employer to reimburse an employee for the cost of medical cannabis because compliance with that order would expose the employer to criminal liability under federal law for aiding and abetting…unlawful possession of cannabis.”

After he lost before the Minnesota Supreme Court, Bierbach petitioned for a writ of certiorari for the Supreme Court to review the judgment in his case.

In his petition, Bierbach offers several arguments to counter the opinion that the policy of reimbursement is in conflict with the CSA.

First, he says the federal and state laws are not irreconcilable. “A reimbursement order under Minnesota’s workers compensation law does not require the employer to possess, manufacture or distribute marijuana in contravention of the CSA. And the Act does not prohibit an employer or insurer from reimbursing an employee for his purchase of medical marijuana,” Bierbach argues.

He dismisses the “aiding and abetting” argument, noting that the marijuana possession is complete by the time of reimbursement and contending that the employer and insurer are merely complying with a reimbursement order. At most, they are “only incidentally” facilitating the possession.

Bierbach further notes that Congress has several times passed appropriations bills with riders that bar the Department of Justice from enforcing federal marijuana laws in connection with medical marijuana programs that comply with state law. This, Bierbach believes, shows that Congress has chosen to “tolerate” the tension between state medical cannabis laws and the CSA.

Finally, he argues that the CSA has no role in regulating insurance.

Thirty-seven states have now legalized medical marijuana, according to the National Conference of State Legislatures. Of these states, six have cannabis reimbursement under workers compensation, with four of them doing so based on a state court decision, according to the American Journal of Industrial Medicine. Another six prohibit workers compensation reimbursement, while other states do not require it or are silent on the issue.

However, the future policy in states may now be subject to change if the Supreme Court enters the fray.

Four state supreme courts in addition to Minnesota’s have issued conflicting decisions regarding the question of federal preemption. The supreme courts of Maine and Minnesota have held—over dissents—that the CSA preempts an order under their states’ workers compensation laws requiring reimbursement for medical marijuana. But the supreme courts of New Hampshire and New Jersey have reached the opposite conclusion with respect to their states’ medical marijuana laws.

The Supreme Court has not indicated the Solicitor General’s deadline for submitting its brief. It typically takes months.