Tests
Not condoning any guys heading to work when they shouldnt, but just exactly how many accidents were attributable to drug or alcohol present in a pilots system... My guess is.... Almost none!
So what is the risk / consequence /probability of this issue causing an accident versus other factors we accept ( mostly) without question such as fatigue, poor training , aircraft that have design flaws with paper procedures that have to be recalled on a dark and stormy night to keep them flying ( ref Airbus) etc etc...
By the way, even though most companies have a zero level, several regulators globally have a .04 BAC in the legislation as well as a 8 hr + bottle to throttle...
So there is not an agreed position or world best practice in the first place...
Frankly give me a "chuck yeager"in a cockpit with a beer under his belt than some of the products from the continued race to the bottom training systems...
But the law is the law so that ends the rhetoric or " gedankan " experiment...