As more states adopt medical marijuana laws, employers with anti-drug policies that expressly prohibit the use of marijuana face a dilemma: can they discipline or fire employees who test positive due to their use of medical marijuana?

The answer in Casias v. Wal-Mart Stores Inc., decided September 19, might surprise you. In Casias, the employee sued under the Michigan Medical Marijuana Act after he tested positive for marijuana that he had taken pursuant to a prescription and was fired by Wal-Mart for violation of its policy against marijuana use. The U.S. Court of Appeals for the Sixth Circuit rejected the employee’s claim, noting that the Michigan Medical Marijuana Act does not cover or restrict employment decisions. Courts in California, Montana and Washington have similarly found that their states’ medical marijuana laws do not govern private employment actions.

So, is that the end of the story? Can employers fire employees who test positive for medically prescribed marijuana?

Dude, get real. The Casias case did not involve a claim of disability discrimination under state or federal law, but in those states where medical marijuana use is legal and has been prescribed to treat a medical condition, employers that fire or discipline their employees for taking legally prescribed medical marijuana can expect disability discrimination claims, reasonable accommodation claims, and possibly other causes of action relating to employee privacy. A related example of this is Fowler v. Westminster College, a federal decision on September 17 in Utah, in which the plaintiff, a recovering painkiller addict, was awarded $300,000 under the ADA after he was terminated because a urine test detected an “excessive amount” of prescription drugs.

Michael Homans is a Labor & Employment attorney and founding partner of HomansPeck LLC. For more employment law updates, including news and links to important information pertaining to legal developments that may affect your business, subscribe to Michael’s blog, or follow him on Twitter @EmployLawUpdate.