Employers doing business in states which have legalized marijuana should make sure that their employment policies are keeping up with a rapidly evolving, and often contradictory, legal environment.

Their employment policies need to reconcile the new state laws, permitting the medical use of marijuana, with the reality that marijuana is still classified as a Schedule I drug by the federal government along with cocaine and heroin.

“Schedule I drugs, substances, or chemicals are defined as drugs with no currently accepted medical use and a high potential for abuse. Schedule I drugs are the most dangerous drugs of all the drug schedules with potentially severe psychological or physical dependence.”

Furthermore, the federal government requires employers to conduct drug (including marijuana) and alcohol testing in safety sensitive industries like aviation and transportation.

Under these testing regulations, the use of marijuana is strictly forbidden anywhere in the United States.

Talk about mixed messages.

So how do employers reconcile these stringent federal laws and regulations with the fact that 23 states (plus the District of Columbia) have legalized the use of marijuana for medical purposes?

In 2009, the Obama administration tried to reduce some of the uncertainties, created by the passage of state laws which contradict federal laws, by issuing a directive to all federal prosecutors encouraging them to not prosecute people who are distributing marijuana for medical purposes in compliance with state law.

Unfortunately, employers do not have a comparable federal directive advising them on how to deal with the use of medical marijuana by employees and most state laws are either silent, inconsistent or vague on the issues that concern employers the most.

While the law in this area is evolving rapidly, here is a short list of what employers need to know about medical marijuana:

1. Employers do not have to permit employees to use medical marijuana in the workplace. The legislation passed in Massachusetts last year addressed this specifically in Section 5, Clause D: “Nothing in this law requires any accommodation of any on-site [my emphasis] medical use of marijuana in any place of employment.”

2.The Americans with Disabilities Act (ADA) does not require employers to accommodate the use of medical marijuana. The Ninth Circuit Court of Appeals ruled in 2012, that because marijuana use continues to be illegal under federal law it is not entitled to protection under the ADA.

3. Employers can act upon the results of a failed drug test if the employee used, possessed or was impaired by marijuana on the job. Even states with clear restrictions on employers (Connecticut, Maine, Rhode Island, Illinois, Arizona, & Delaware) regarding discrimination against medical marijuana patients have exceptions which allow for termination under these circumstances.

4. Employers can also terminate an employee (with a prescription for medical marijuana) who fail a drug test for marijuana if failing to terminate would somehow jeopardize the employer’s “monetary or licensing related benefit under federal law or regulations.” In other words, employers who have federal contracts or are otherwise subject to federal regulations are not required to change their policies concerning marijuana.

5. Organizations not subject to federal regulations should review their substance abuse policies to ensure compliance with state laws, particularly in those states (see above) that have clear restrictions regarding discrimination against medical marijuana patients.

6. Employers thinking about establishing a drug testing program need to consider that the passage of medical marijuana laws means more employees will be using marijuana outside of the workplace. You can expect more challenges from employees who fail a drug test for marijuana but claim they were not impaired while working.

7. Employers should train supervisors and managers to recognize the signs of impairment (whatever the source!)

8. Employers should train their supervisors and managers to respond properly to inquiries from employees regarding the use of medical marijuana. Employees who are hearing that marijuana is now “legal” may be confused about how these new laws may effect their employers policies and procedures.

Employers bear a legal responsibility, under the general duty clause of OSHA regulations, to maintain safe work environments.

The passage of state laws legalizing the use of marijuana for medical purposes has complicated, but not in any way reduced, that obligation.