I proposed my catch-all solution for this in another comment: https://news.ycombinator.com/item?id=26183297
My ideal is we just ensure competence - guy who smoked weed last night may be more competent than a clean guy getting divorced. Test the competence
It would be great if there was a way to test for competence. Some drugs cause long term issues with decision making and being able to see what's likely to happen. This reminds me of a job I had years ago framing houses. I remember some of the work men firing nails from a nail gun into a nearby woods. An area where neighborhood kids happen to play.
That's poor decision making and a liability. How do you test for complex things like that?
Film the worksite or send surprise inspectors to catch workers too lazy/reckless about their nail gunning. Maybe show them videos of nail gun injuries!
Improper nailgunning I think is more related to ingrained attitude than ephemeral competence degraders (drugs)