Since it's not, TheStickman was correct in saying, "States legalizing medical cannabis or outright full legalization is in keeping with the 10th Amendment" (as is states outlawing cannabis within their borders).
I don't support liberatarian pot-heads working to change laws that only hurt Americans young and old.
The federal government can't rightfully enact laws outside its Constitutional authority, even for the purpose of preventing hurt to Americans young and old.
And since young people have been reporting for many years that they can get cannabis more easily than beer or cigarettes, it seems that it's banning cannabis for adults that hurts young people - by putting cannabis in the black market, beyond the reach of effective regulation such as age limits.