Explain why the idea that people will prefer illegal weed to legal weed is unlikely.
Sorry this is just a silly answer. 
First, WHY do you think that - just your gut? You think they'll prefer illegal weed to legal weed? They'll prefer breaking their law to meet up with their dealer than to walk into the dispensary and order from 20 available varieties? 
I'm sorry, but I doubt you've thought about it at all.