A necessity does still not make it a right. My company, my rules aside from the ADA and a few other constraints.

I hate to get Bone started, but here it is: Casual toker software geek gets in his car and leaves IBM to go pick up some nerd stuff to finish a project and on his return to work plows into a 3 y.o. At the hospital, he tests hot for pot. IBM has no drug screening policy, so they get nailed for negligence in allowing a guy who they have not screened operate a vehicle during his course and scope of employment.