It's simple. Have the feds point out in the text of the Constitution the enumerated power to control what substance any of us wants to put into our bodies. Since it's not in the Constitution, then they have absolutely no say on the matter. Any federal law not made IN PURSUANCE of an enumerated power is null and void. It's reserved to the states and the people as per the Tenth Amendment. And as such the state has a duty to defend the rights of it's citizens against the federal government's unconstitutioal acts.
Truth. And on top of that, they cant stop an entire industry ready to go, not when the people realize how much better it is for them and their communities, no more kids just getting ahold of it, unless they take it from their parents or older bro.