Not one of the delegated powers to the United States, Article I Section VIII.
Terminate it!
The whole drug prohibition regime is sketchy.
It used to be that this matter was a matter of concern to doctors and preachers. Which is how alcohol should have stayed, with optional local limitations on sales but not on ownership. Prohibition was not a conservative idea; it was a progressive idea. It is now a tiger that we are riding and that we can’t see any safe way to dismount.
We’ve virtually forgotten about the preachers today. The people who kept warning us that drug abuse is a method that the devil uses to ruin lives that could otherwise shine for the Lord’s sake. But the preachers were why we had few drug abuse problems in America in 1900.
If we are merely secular, there isn’t going to be any good way to keep the hazards of drug abuse at bay. At worst we can have fig leaves. We can crack down arbitrarily on street drugs, but then doctors will prescribe mother’s little helpers.
A drug problem is really a no-God problem. People refusing to embrace God and looking for illusions to fulfill their craving for what is transcendent.