I assumed a rational meaning in your first post. Sorry.
My mistake.
Also, As far as the government is concerned, the devil's in the details (or in this case, the same government that is woefully failing to secure the border and stem the drug trade coming from Mexico(in this case)is the same government that would be responsible to collect taxes and somehow turn it into a victimless extension of free enterprise.
I wish it could be that "live and let live" simple, but I know it will create more bureaucratic problems and tragedy than it will ever solve. Besides, the Mexican drug lords will just undercut the retail and tax costs by offering their wares at cheaper prices in a tax free black market environment. I guess the IRS can go after them then instead of a non-existent DEA, but they can't/won't even collect income taxes from the other 50% of our population now that's supposed to be paying taxes, so I don't have much faith and confidence in their ability to enforce the plan you propose.