Crime benefits from network effects even more than regular businesses, you have to attack them via every opportunity.
However you are putting words in my mouth, in a typical American style of prosecution-->banning. It is quite possible to legalise and regulate marijuana. American halfway legalisation creates an industry which funds OC and can't be prosecuted. Canadian legalisation creates a revenue source for the provincial governments while providing vertical integration and control, and the volume of illegal weed has plummeted.