boy, do YOU have it backwards... the feds cannot pass laws OTHER THAN their enumerated powers- and drug use is not one of those- each state has a right to make its own policy and laws for drug use.
There is nothing in the constitution that says federal laws trump all state laws- ONLY the enumerated powers.
The civil war was not fought to establish federal supremacy (well actually maybe it was) but it was WRONG. The states had the right to withdraw from the union. Preserving “The Union” was not some sacred thing...
imagine if they had fought over something OTHER THAN slavery, like the fed government telling you you had to buy health insurance, for instance.
No they don't. No more than they can authorize the importation of nuclear material or chemical weapons. Drugs are chemical weapons being used against the American populace. I note that "chemical weapons" are not specifically enumerated in the constitution, but they are easily within the blanket coverage represented by the defense clause.