I'm probably in the minority in that I'm over 50 and have never had a beer or marijuana or any other illegal drugs. So, my only experiences with any of them come from my childhood...living in a home where some of those things were a problem. All that said, marijuana being illegal is simply insane...especially for medical use. The NFL testing for it in no way improves the image of the league or the product they put on the field. I believe it is counter-productive.
If there are issues of a substance being abused, they need to treat those things as medical issues. Having watched it, I think abuse is more medical than behavioral at its core.