Your rights vs. your best interest
The wisest among us understand an immutable law of nature: just because we can do something, doesn't mean we should. There are lots of times when we are presented with options or pressed to make a decision and, though we desperately want to go with this, we defer to that, because we know to do otherwise defies that immutable law.
To wit: just because I can wear a bikini (i.e., I am well within my rights to wear whatever swim attire I choose) doesn't mean I should.
The same goes for employers when it comes to their drug-testing practices and drug-free workplace policies, especially as these relate to soon-to-be-legal medical marijuana. Just because you can have a zero-tolerance policy towards pot, doesn't mean you should.
A recent article in the Columbus Dispatch, Many Ohio employers likely to bar medical-marijuana use, highlights the decisions employers are contemplating in advance of medical marijuana becoming legal later this year.

This is a controversial topic, of course, and there are no easy answers. Further, I am not advocating for drug use, and certainly not during business hours. Nonetheless, I counsel my clients to think differently than they have in the past about drug testing.
A zero-tolerance drug policy is well within their rights. But is it in their best interest?
For some occupations, zero-tolerance is not just wise, it's mandated (i.e., machinist, pilot, driver, surgeon, etc.). There are both laws and policies in place to account for behavior and conduct in those occupations. Those should stay in place, no question.
But for the vast majority of jobs, employers need to consider the implications of zero-tolerance on their ability to attract and retain their best workforce. If they're already struggling with workforce, it's probably counter-productive to further narrow the pool of workers.
Employers get legal advice from their attorneys. Their HR department ensures employers stay in compliance. CFOs mostly take the position to advocate for money-saving policies. Too often, however, no one guiding employers on how policies, like zero-tolerance drug testing, will impact their current and future workforce.
Andrea J. Applegate is president of Applegate Talent Strategies, LLC, a firm that advises employers on their people practices to ensure they can attract, retain and engage their best workforce.