In Arizona a few years back they make drug testing mandatory for Taxi/Livery/&etc drivers so I looked up the law after the owner of the company told us "look, the law says I have to drug test you guys but it doesn't say you have to pass so just bring it in and I won't even look at the results."

Nothing disqualifies you as long as they have documentation of a background check and drug test -- axe-murdering crack head with a penchant for buggering small animals, perfectly legal.

The governor got some flack for that one...