You do realize how stupid what you said is, right? It's already illegal (most places) and growing it can get you serious jail time, even if making it legal resulted in what you said it wouldn't actually change anything for the people growing it (they're already breaking the law now so if it's illegal to grow without a certificate then anyone without one would be growing it illegally... Just like they already are), except that there would at least be an option to do it legally if you can afford it, and people buying/selling it aren't criminalized and vilified the way they are now. Legalizing it is an outright and unequivocally good thing to do in every respect.