First off: if weed is illegal; tobacco, alcohol, and caffeine should be illegal too because they are equally as dangerous or more dangerous.
The legalization of weed would regulate it, which would lower the use of children obtaining it. It would eliminate the need for a black market for weed. Drug lords would take a huge hit on profits. The taxes would help improve schools and roads. We would spend MUCH less tax money on inmates because Prisons wouldnt be nearly as crowded.... I could go on for days but im stopping here