Can I be fired for using cannabis in Missouri even if I have a medical marijuana card?

Amendment 2, Sec. 7(1)(d) says that cannabis patients can't "bring an action against any employer, former employer, or prospective employer for wrongful discharge, discrimination, or any similar cause of action or remedy based on the employer, former employer, or prospective employer prohibiting the employee, former employee, or prospective employee from being under the influence of marijuana while at work or disciplining the employee or former employee, up to and including termination from employment for working or attempting to work while under the influence of marijuana."