Yes it should be legal. Unlike alchohol or tobacco the drug itself has never caused a death. The effects of marijuana may impare motor skills, but so does drinking alchohol and alchohol can kill you just from drinking it. It's not as addictive as either other substances previously mentioned (alchohol/tobacco) and if agents of the law weren't so busy looking for someone rolling a joint in their back yard maybe they could put more money into things that matter, like homeless people or finiding Ben Laden.
I think if it were legalized to sell then you would be required to have a license to sell it. It could only be sold in appropriat places and the age on it should be either 18 or 21.

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-Oz