I question regulating it for adults, even at the state level. Our governments should not think they have the power to act like our nannies. Educate, rather than legislate!
The problem is legalizing it will expand the government exponentially. Why do you think George Soros is supporting? Because it's the step that will make the U.S. government socialist, and bring ubiversal healthcare. Just imagine, the U.S. government is the world's largest drug dealer.