We also ask if they are smokers.  

We just went through renovating a cigarette smoker cat spray house (an inherited tenant) and after 3 full scrubbings with TSP, soaking slab and subfloors in vinegar several times over several weeks, then painting subfloors with Kilz, duct cleaning, etc., it finally seems to be resolved.  

Pot smokers always say they aren't smokers.  

:) The plastic blinds will likely be stained, particularly in the room(s) where they smoked most frequently.While folks will suggest to prime with a sealant primer (such as Zinnsser), if there have been long-term smokers, it may not be sufficient - it will cover in the short-term, but the toxins will eventually find their way to the surface again.We helped to renovate a house where the prior owner had been a heavy smoker for 30+ years.  

Landlords may not want a pot smoker, but it's going to be tough to discriminate in the not too distant future.  

I also don't allow smokers, do you smoke?

Scenarios of subletting, huge amounts of family members moving in, unlisted pets, AirBNB deals under my nose, multiple calls for trivial issues, smokers, hoarders, etc.

I say "should" because there's always the chance the judge is a recreational pot smoker or just sympathetic to their cause. 

If you see them smoking in their car before they come to meet you, you can deny them because they are smokers (if that's in your criteria).So, have tough criteria, and apply it evenly to everyone, and you will not likely have to ever rent to a Section 8 tenant.

I can discriminate against smokers by saying "no smokers allowed".