I've never understood how this kind of thing has anything to do with your Federal Government.

I gather it's to do with "interstate commerce" - but how is that relevant any more than it was in the case of booze,when it was legal in some states and illegal in others? Federal Prohibition necessitated a Constitutional Amendment.

Has the current Federal ban on dope ever been tested in the Supreme Court? On the face of it, it sounds highly unconstitutional.