Legalization.
- It will be taxed of course, creating copious amounts of revenue for a government.
- Has medical usage, ranging from aid in coping with pain to helping one sleep.
- Money and prison space will no longer be wasted on people convicted of possession.
- People who only smoke weed will no longer have to go through dealers, which could lead to them trying harder, dangerous drugs.
- I imagine hemp would be legal as well.
Hemp is nice.
- Not anywhere near as damaging as nicotine; the effects of being high are much less severe than being drunk.
Finally, for the regular person, it's a nice little thing to have at the end of the day, when all responsibilities are taken care, to just sit down and smoke a little to relax, and enjoy life a little more.
tl;dr, literally no reason for it to continue being illegal.