In the existing reality, this method is still preferable to the current status quo as it would be effective still. You aren’t going to stop racism by legalizing drugs but you are going to let many, many innocent people be killed and exploited by junkies and the seller gangs and cartels. Clearly ignoring the problem isn’t working so stepping up the game is the next step.
If someone refuses help then it doesn’t matter, as long as they are kept away from the rest of society. Jail/labor camps would probably make the most sense. If someone doesn’t want help then you can’t help them even if you try