It was about states rights, the right just happened to be slavery. But, a state should be able to govern itself. The duty of the federal government is to provide an army for protection of the state, and subsidize road projects etc. If a state wants to have legalized marijuana, the federal government shouldn't be able to come in and supersede that law. It's like the government treats its states like the foreign countries we deal with. You either play ball the way we want it, or you get no aid.