There is no Constitutional authority to prohibit ANY drug, and the whole war on drugs is absolutely ridiculous. During Prohibition, the murder rate doubled. And today most crime is either "drug crime" or things people do to get more drugs (because when they're black market, the price is far higher).
But even legalizing marijuana altogether would be a good first step. They waste an untold amount of money and resources on this, when prescription drugs are far more dangerous.
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Google isn't as dumb as you think.