You are free to tell employees they can be terminated for having marijuana in their systems and then randomly test for the substance. That’s true even if a doctor recommends that the employee use medical marijuana.
Just make sure your policies state clearly that medical marijuana use isn’t allowed and that it doesn’t matter whether a doctor has recommended its use.
Recent case: Joann worked as a correctional officer at Pelican Bay State Prison.
When hired, she received a copy of a drug testing policy that warned her about random drug tests and specified that testing positive for marijuana was grounds for termination. Later, after medical marijuana use was approved in California, the department issued a new memo that clarified a prescription was needed for any controlled substance use and that because medical marijuana wasn’t “prescribed,” but was “recommended,” it didn’t qualify.
Still, Joann got her recommendation and began using marijuana to treat insomnia. When she tested positive during a random drug test, she was terminated.
She sued, noting that her marijuana use was legal in California under state law. She argued she should not have been fired for engaging in a legal activity.
The court rejected her argument and said the employer could set its own rules, including only excusing prescribed controlled substances. The case was dismissed. (Morrison v. State Personnel Board, et al., No. C069749, Court of Appeal of California, 3rd Appellate District, 2013)
Final note: Remember, you get to set the rules. Just because something is legal doesn’t mean you have to accept its use at work.
No court would expect you to allow an employee to show up intoxicated after drinking alcohol, a perfectly legal activity. The same goes for marijuana.