Tenant with medical marijuana card. What are my options?

[Josh Ball]

I've got a long term tenant lined up & the unit is a non smoking unit, which the applicant is aware & fine with for indoor. He disclosed that he has a medical marijuana card but would only smoke outside. 
Some of the neighboring tenants are older & I know they're going to have an issue if this guy is out back smoking marijuana. I could care less if someone smokes marijuana but worried it might impact other tenants & future renters.

What are my options, if any? Can you deny someone's application based on this despite it being a medical marijuana card & not technically breaking the rules of smoking indoors? If you've been in similar situation, have you found it brings an issue down the road with future tenants or current?

Thanks in advance.