The rule on legality - clarification state V federal

There’s currently a thread here asking for advice about the best medical marijuana dispensiary in Seattle, or something to that effect. As I understand it, that is entirely legal by state laws, and entirely illegal by federal laws.

There are fairly strict rules on SDMB about threads discussing illegal activity by the OP, with threads closed even if the activity is legal in wherever the OP is, but illegal by US laws. So with a thread as I mentioned, where state and federal laws conflict, what is the ultimate deciding line? If it is illegal anywhere in state/federal? The defacto enforcement situation? The common-bloody-sense line - easy with pot cause no one with a brain thinks it should be illegal but this could be different with other laws*? Something else?

It’s kind of a pointless question for me to ask in a certain sense cause I can’t imagine I’m going to be starting a thread that will be affected by it any time soon; but on the other hand I actually think it’s an interesting question so I would be interested to hear views on what the rule ought to be as well.

*For example firearms. You can justify almost any position on them and I understand there to be state V federal conflicts galore here.

I think that thread got sent to the cornfield. That may be your answer.

Let us get back to you on this, please.

Nope - actually it’s been moved to here by a mod.

Okily dokily.

Another interesting question that occurred to me - what about things that are legal in one state but illegal in another?

We do tend to take things on a case by case basis. Guess that would also be true for state vs. state.

The thread in question has been asked and answered, so we’re good here too, I think.