Actually, I think that the drive to make hemp illegal was spearheaded by William Randolph Hearst.
Hemp makes good paper and is cheap to raise. Hearst owned vast tracts of timber. If he could make the growing of hemp illegal, then his timber would be worth a fortune as paper pulp.
He did and it was.
Scope out such propaganda films as 'Reefer Madness".

troll *not bad for an old conservative, eh?**