A very good friend of mine is one of the top reggae percussionists in the world (was Jimmy Cliff's percussionist....). MOST reggae performers and even Rastafarians do not smoke pot. It is a big selling point because of Bob Marley's public embracing of marijuana. Having spend time in Jamaica, in places in and around Kingston that most people perceive as ridiculously dangerous, my family and I have had remarkably healthy and enlightening experiences with some very spiritual, kind, healthy people. I am looking forward to taking my family back to Jamaica again for this holiday season.
Back to the issue you raised.... In my younger hellion days, I was certainly no angel with drug and alcohol use. Even then, I would remain sober when competing at high level athletics. Depending upon the drugs that you are on, your performance can be artificially enhanced (the number of baseball players who have ADHD
and take medication for that- speed, is statistically far beyond stat.s from the general population). The downsides with some medications can appear when they have underlying physiological conditions (weakened artery...) and the damage is subtle until it typically becomes suddenly severe and life-threatening. Other drugs, like marijuana (NOT tested for in the NBA, because they would likely not be able to field teams!) do like you say and people think that it makes them focus better, The reality has been tested too many times that people should simply give up on that argument.
detection: Pupil response is a GREAT means by which we can get a quick and relatively accurate read of whether someone is on pot, speed, opiates,....
I allow adults to act like adults. If you want to play game, be willing to live by it's rules. One of my rules is based upon personal experience, best science and sports practices, which means that sobriety in my dojo is a strictly enforced rule. I have no problem asking people to step off of my mats and talk with me if they seem under the influence of anything. Sometimes a student has had a couple of beers and is on the mats six hours later and I smell alcohol on that person's breath. I then speak to that person privately and then make my decision. I have no problems helping people with abuse and dependence problems (no me personally, because it would be an ethical violation as a psychologist- dual roles).
I am genuinely glad to see endorse sobriety. I am not surprised by that, but then again not many of us White folks attend indigenous, religious ceremonies in some of the poorest neighborhoods in Jamaica either (amazing experiences). First impressions are what they are. It is the ability to look beyond what we see that truly allows us to deepen our life experiences.