With rare exceptions, employees cannot be terminated because of a medical condition or the medicines that they take for it. Employers are required to make “reasonable accommodation” under the Americans with Disabilities Act (ADA) for such situations.
One exception is the use of medicinal cannabis. Though it is now legal under Maryland law, there is no accompanying law protecting workers who are using it. There have been no court cases to assert workers’ rights. It is also still illegal under federal law. For those reasons, a worker who fails a drug test may not have rights even with a valid certification.
Current status
Last December, cannabis dispensaries were finally authorized in Maryland after many years of delay. Patients registered with the Maryland Medical Cannabis Commission (MMCC) and certified for treatment could finally begin purchasing medical marijuana after years of delay.
Unlike some states, Maryland has no corresponding laws regarding drug tests or other provisions. Pre-employment drug screenings are still allowed to prohibit employment even with the certification. There are no other laws protecting workers who have come to rely on medical marijuana as part of their treatment.
This is unique among medical treatments for that reason.
Federal employees especially at risk
Despite its legal status in Maryland, marijuana is still illegal under the federal Controlled Substances Act. For that reason, it can be grounds for termination of federal employees. To date, there have been no challenges and it remains to be seen if there will be.
In general, it should be assumed that federal employees have even fewer rights to medical marijuana regardless of any state laws.
If you are challenged
This is clearly an issue that is waiting for either more clarity from the state legislature or the courts. There is likely to be a case challenge some day. Until that time, employees should presume that their certification for medical cannabis will not protect them from adverse action by an employer.
If you are in the position of facing disciplinary action because of your use of properly licensed cannabis here in Maryland, you should talk to an employment attorney about your situation. It is a very unclear area of current law, but you do have rights.