As a lurker on these posts for years, I don't think it has anything to do with changing the minds of one side or the other.
The answer to the question of, "How does that work?", is which side brings the best legal arguments.
In that light, if I were the judge of the debates, the 'winner', hands down, on the constitutionality of the federal laws prohibiting marijuana use is the PRO crowd.
I can find nothing in the constitution enumerating this power to the feds.
Which of course only de-legitimizes the FEDERAL WOD. The second prohibition would be just as wrong even if it was only prosecuted on the local or state level.
Legal arguments are just one facet. There is a question of fundamental individual rights which is far more important.
Our little friend Robby asserts that there is a right to have others do or not do as he sees fit even if they are not violating anyone else's rights.
He claims a "right" to raise his children in what he considers a perfect world.
In my view, such a right could be exercised against his existence since I would assert my right to raise my children in a world where tyrants like him who seek to overpower others to their own bizarre will should not exist.
Of course, such ruminations are childish.
Ah. What were you looking under, "drugs, regulation of"?
Well, the U.S. Constitution isn't that specific. Sorry.