I can't believe it took 16 responses for someone to say this. All pot sold at dispensaries has to be grown onsite or by a commercial grow under the dispensary's MIPS license.
They aren't allowed to just buy product from randoms off the street, and I don't expect this to change much with 64's implementation.
Also, you can be sure you'd have to fill out paperwork to sell to them. What do you say when the Feds come knocking on your door asking about that 12 lbs you sold the dispensary up the street last month without any kind of license?