[El Cid]

He just wants to make his largest export legal.

I don't have a problem with that. Its a weed, and it if its legal, the price should drop 10X to 100X (I don't know the specific economics, but if its a weed, it ought to be cheap).
I, for one, like the idea of cratering the profit margins of the scum that sell this stuff.

[Eagles6]

The gubmint would just tax the hell out of it, the price would remain the same and the black market would remain. Look at tobacco and booze in high taxed states. The cartels would shift their resources to smuggling more cocaine, meth, ecstasy illegals and weapons.

Mexico decriminalized drugs and that hasn't worked out too well for them.