Why is Marijuana still illegal when some legal drugs are more dangerous?

I feel it is unconstitutional to pick and choose one drug over the other in this country, especially when Marijuana and Alcohol have been proven to both cause cancer. Where in the constitution does it say the government can police your personal habits as long as it doesn't violate other people's liberties?... show more I feel it is unconstitutional to pick and choose one drug over the other in this country, especially when Marijuana and Alcohol have been proven to both cause cancer. Where in the constitution does it say the government can police your personal habits as long as it doesn't violate other people's liberties? I thought conservatives would be extra happy in legalizing all drugs for that matter!
Update: *EDIT: I meant Tobacco and Alcohol*
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