This is true; the problem though is that people have been indoctrinated/conditioned to think that the War on Drugs is a Good Thing™ — despite the fact that it is entirely contraconstitutional and destructive to the majority of the Bill of Rights. In short, it is impossible to be a Constitutionalist and support the War on Drugs.
(The only amendment from the Bill of Rights that hasn't been weakened/destroyed is the 3rd.)
Same goes for intrastate abortion, intrastate gay marriage, intrastate sales tax, intrastate income tax; intrastate minimum wage, intrastate amnesty for illegals...
I share your concern about the Bill of Rights in general. But I do think that federal government has a role to play if hard drugs are pouring over state and federal borders along with hordes of cartel thugs.
And don’t tell me that legalization will make cartels go away. As the quasi-legalization of drugs in the Netherlands proved, some things will always remain illegal and cartels and organized crime will always be there in the shadows.