I don't think the NCAA, an individual university, or even a pro sport should be testing for anything other than performance enhancers -- period.
I also think it's insane that we test people for jobs, even those operating heavy machinery. All a job seeker has to do is test clean on hiring and they're fine. Americans should never, ever, have given employers the right to violate their privacy like this and those very same urine tests can be used to screen other things too (like medical issues). The only time drug testing in the workplace makes sense is directly after an accident where the accident is suspect and those can be performed instantly nowadays. After a few weeks on a job where drug usage matters to performance most employees can tell you whether or not someone is using at work.
I don't use illegal drugs but I don't give a crap what someone does on their days off or evenings off. It's not my business and if it's problematic abuse it shows up fast at work even when they're not using during work hours (doesn't matter if the abuse is pot or alcohol - if it's reached problem status and they only use/drink when the clock strike 5 you'll usually know it).
If they have a real substance abuse problem and can hide it at work, and some can, they can carry on their merry way. That's for them and their family to sort out.
And for the record drug use/alcohol use does not = abuse.
We're making a whole lot of people rich while wasting a whole lot of money buying into what the piss test industry is selling - an industry that has grown exponentially since the late 80's and early 90s.