Well... Monsanto could get into the industry if they want it. Kinda like how some guns are banned in California but not others. I wouldn't be surprised if Monsanto already has subsidiaries in each state growing pot.
From what I've heard about the retail sector of pot, the pot shops that are in good with the local government will send cops to harass customers smoking outdoors around competing shops. That was one of the reasons why I never moved to Portland. I wasn't in good with the community enough to assure I wasn't gonna get pushed out. Plus, Oregon also evoked Colorado's policy of requiring two years of residency in order to even apply for a permit to handle cannabis. Gold rush prevention policy.