Federal law overrules local law, so they are intertwined. A vote at the federal level is in many ways a vote on local laws, too.

While technically true, this isn't always the case in practice. After all, marijuana is still illegal in the eyes of the Federal Government but this has done very little to deter state-sanctioned dispensaries in more than a handful of states.

That means it sometimes is the case in practice.

I wasn't disputing that. I was pointing out that there are notable exceptions.

Okay. I guess I'm saying that's irrelevant. For local & federal law to be intertwined doesn't require there to be a lack of exceptions.

Not fully. It's already pointed out that federal law overrules state law, but it's important to remember that congress is only supposed to be able to make federal law on a small set of enumerated issues. IMO the issue is when you have an expansion of what congress is able to make laws on which limits what states can do.