Individuals simply have to enforce their own rules. If your kid uses pot throw them out. Don't let it in your home or your life. Practice shunning. Call the police. File complaints against your neighbors. Start some trouble. Work for bans in your city, homeowner's associations, apartment buildings, offices. If it's legal just hound them away until the only place they can be is their own little cities. Treat pot like cigarettes.
All this rolling over because a few potheads got a vote in two states is silly.
I bet you're one of those Mormon freaks.
Shunning works quite well, and you don't have to be a Mormon to do it. If you like, call it ostracism. Does that sound better?