Mark's caution may well be warranted. some cases out of California upheld an employers' right to fire employees using medical marijuana since it is still illegal on the federal level or was deemed to impair the employee's ability to do the job. My experience has been that employers routinely callously fired employees needing medical attention regardless of the potential legal consequences. There is no absolute legal "right" to take even prescription drugs and work. It was horrendous for the employee even if his/her complaint made it through our bureaucracy up to my level to handle. At least a year had gone by, with no salary - unemployment denied- and cases were hard to win due to the requirement that the employee still had to be able to do the job with only "reasonable accommodation". Drug testing failure was always a loser if they tested positive for any illegal substance. Private attorneys are usually reluctant to sue unless they are being paid and contingent fees are mostly in the personal injury (car accidents, etc)unless they involve a class action component. Bottom line, Mark's employer would probably get away scott free, so I have to go with Mark's analysis here.
Eric, you are a pistol though, but the "f' word alone would then justify the employer firing you and that would stick. Judges are not sympathetic to pot users or "disrespectful" employees. Back in the bad old private practice days, the saying was " How much justice can you afford?"
charm