Medical Marijuana In The Workplace

With the recent expansion of legislation permitting the production, sale and use of marijuana for medical purposes, employers should begin to think about crafting a policy which addresses medical marijuana use in their workplace.

For example, the smoking of regular cigarettes is not permitted in buildings or near entrances and exists to buildings.  Employees who want a smoke usually need to head further afield during their breaks.  But is it proper to ask the same of employees who are smoking medical marijuana and may have a disability?  Is it proper to make them smoke in the presence of others, so that their disability is no longer a private matter?  Is it proper to have regular smokers ingesting medical marijuana smoke if all smokers are required to smoke in the same area?