Many of my Texas clients also have offices in Colorado. Since that state legalized the recreational use of marijuana in November, I’ve begun receiving questions from my clients with locations in Colorado about their workplace drug use and testing policies. They want to understand their rights in light of the legality of marijuana in that state.

Legalized marijuana should be no more difficult for employers to handle than alcohol. If an employee is drunk on the job, you as an employer have a right to test him and to fire him for reporting to work under the influence of alcohol. An employee who is high on marijuana at work presents the same issue. However, marijuana shows up on drug tests long after the body has processed and gotten rid of alcohol. In other words, an employer testing on Monday won’t know that the employee was drunk on Friday night.  But if the employee got stoned on Friday night, testing on Monday will reveal that fact. Employers are therefore concerned that they won’t be able to fire an employee who tests positive for marijuana use but can’t be proven to be high at work. This generates anxiety for safety-conscious businesses.

At this point in time in the Fall of 2012, marijuana is still illegal in the United States, and therefore in every state. Just because an employee isn’t in violation of Colorado state law by smoking weed, he is still in violation of federal law and can be in violation of the employer’s substance abuse policy if it is well-written. Therefore, as an employer, make sure your policy states that, along with being under the influence at work, the use, possession or sale of illegal drugs is prohibited, and illegal drugs should be defined as any drug that is illegal under municipal, state and/or federal laws.

The federal Department of Transportation announced in December 2012 that state legalization of recreational pot would not change the rules prohibiting marijuana use by employees in safety-sensitive positions such as truck drivers, pilots and school bus drivers. Therefore, explaining away a positive test for marijuana by saying it was used legally in Colorado will not be an acceptable excuse and will still subject truck drivers, for example, to suspension of driving duties. Employers can take the same approach by letting employees know that the employer’s safety requirements will not be affected by state laws legalizing marijuana and that employees will still be subject to discipline up to and including termination for any drug test that shows marijuana use.