If they made weed legal, you would only be allowed to buy from licensed pharmacies, even then, it would be illegal to grow your own pot.
Why? Because the government won't be able to regulate and tax it if some bumfuck is growing it in his closet. In which case the government gets no money, thus, there is no incentive for the government to legalize it.
Already there are stoners protesting the governments where pot may become legal because they say that the government can't tax their
home-grown weed.
Of course, the government has the moral upper-hand because like
>>3 said:
It is a powerful narcotic with a potential for abuse.
In this case the government has a proper reason for wanting to regulate (and tax) marijuana the same way they regulate any other legal narcotics.
So protesting stoners can go fuck themselves and better realize they're gonna have to smoke with moderation and purchase their pot from the pharmacy. Not that they have to, once pot becomes legalized, it will be
IMPOSSIBLE to find illegal weed gardens since everybody will probably be smoking it and since it can be grown indoors, it will be impossible to enforce anything related to weed.