Answer:
The government forbids marihuana essentially for two reasons:
The arguments above, while not fully invalid, are not strong enough to continue the support of marihuana ilegalization. While marihuana can be harmful, and addictive, it is not much more harmful than other legal drugs such as alcohol or tobacco. Besides, it does have many medicinal uses, and finally, several states have decided to legalize marihuana and the experience has been largely positive (for example, Colorado).