Back when alcohol was illegal, everyone said that it would increase crime to legalize it. However, there was a lot of bootlegging - similar to how there is the illegal drug market today.
Legalizing marijuana would help keep money in the US instead to the Mexican drug market.
On the other hand, there are a lot of issues that aren't ironed out such as how to you enforce smoking/driving laws, workforce issues, and more. In addition, a more comprehensive method to tax sale of marijuana is needed as well.
What are your thoughts on prop 19.