Legalize it.
You already came up with the pro's and i don't think there are any con's.
It should be done as in Holland. A max. of lets say 3g can be bought per day and person. Required age 18.
No smoking and driving.
But actually, i don't really care. There are enough ways to buy it here, and Holland is about 1,5 car hours away. You get what i'm on about.