Frequently asked questions What are the medical marijuana laws in Missouri? Here is an overview of the medical marijuana laws in Missouri: 2014 – CBD oil legalized to treat persistent seizures. 2018 – medical use of cannabis legalized with 66% of the vote July 2019 – Applications for medical marijuana start being process. The state will have 30 days from the patient’s application to decide whether the patient qualifies for medical cannabis. August 2019 – The state starts evaluating who qualifies for growing/cultivation, infusion, dispensary and distribution licenses.