We don't have accurate ways to test if you're high though. We can only test if you've done it in the past few days/weeks.
Fire someone for showing up to work drunk, sure. But would you fire them for a bottle of wine on a Saturday night?
Fire someone for showing up to work drunk, sure. But would you fire them for a bottle of wine on a Saturday night?
If alcohol was like THC (that is, it's impossible to determine whether you drank in the last hour or the last week), I sure as hell don't want people who test positive driving.
That, plus marijuana is still illegal in most states. Whatever your personal conviction may be, businesses aren't in the business to turn the blind eye to illegal substance use. They're on the hook for liability.
NPR recently pointed out that if you include medical marijuana this is no where close to true with it being legal in 29 states: https://en.m.wikipedia.org/wiki/Legality_of_cannabis_by_U.S....
So as far as I know, there isn't a reliable and accurate way of testing.
Roadside DUI test is a general test for motor impairment. BAC tests are a nice proxy for that in the case of alcohol, and a legally convenient one as they are precise and objective, but the police care (morally speaking) about your motor impairment not your BAC.
tl;dr, we can already answer the question "is this person too stoned to drive?", roadside DUI test.