the problem is that the federal government is decriminalizing drug use, and that it's largely following the direction of the courts, and this is in fact largely correct. if you own your body, you have the right to abuse it any way you want, including pumping it full of poison. and, really, if you can afford it and aren't bothering anybody, who has the right to tell you to stop? nobody does.
the problem is when you can't afford it, and resort to crime to pay for it, and when you are bothering somebody, like taking over streets and yards. so, you need to criminalize those activities, and then arrest people and charge them for it, and then you need to strengthen those sentences. then you need to give the addicts treatment as a way out of jail, in terms of bargaining with them. that's how you get them into treatment, you tell them the other option is they go to jail, and then you follow through and send them to jail if that's their preference.
you're never going to convince the supreme court that this is legal, not even with an oakes test.