No, the black market would become a new growth industry because people wanting to avoid the $50.00 per ounce tax would still prefer to continue giving the profit to the drug dealers rather than to fuel the government police state... it would be less expensive to give the profit to the drug dealers...
Medical marijuana is the same story... There is a huge proliferation of news stories about "medical" growers being arrested because they have more than their government allowance of pot...
Why anyone in their right mind (provided they aren't stoned all the time) would want to register with the government as a pot smoker with their little medical marijuana card and draw attention to themselves, is another question of government intrusion invited by an unsuspecting, uninformed public about the powers of government intrusion into personal privacy.
The better idea would be to just get out a big eraser and wipe all the marijuana laws off the books and stop feeding the ever growing police state.
What $50 per ounce tax?
Marijuana should be taxed like tobacco, more like $1 an ounce.