I was wondering about that... if that drug is legal in my state (OR), can I discriminate in hiring against those who use it? Screen for THC even though it is legal?
I agree about DUI. They will have to be able to test for impairment, establish legal limits, etc.
Since it is legal to not hire tobacco smokers it should be doubly important to be able to exclude pot smokers. In fact it would be a marketing bonus. It may also be a liability insurnce REQUIREMENT to exclude pot smokers.
There is no DWI/DUI pot test for the roadside. Generally, the pot smoker simply drives impaired and kills pedestrians and other drivers. The most efficient solution is to pull the license of medicinal pot users.