<<North Korea has just announced that all actions by any nation to enforce the orders of the UN will be construed as an act of war by the US>>
Since the UN has never ordered any actions enforced against the U.S., we have no way of knowing whether this North Korean policy is in any way similar to any U.S. policy. There IS no U.S. policy dealing with how to react to the attempted enforcement of UN orders against it.
Although it gets tricky - - they already ARE at war with the U.S.; have been since the armistice that ended the shooting phase of the Korean War. If the U.S. commits an act of war against Korea, it might be a breach of the armistice, which would leave North Korea free to resume hostilities. Does the fact that the UN ordered the sanctions make them legal? What if North Korea FAILS to appeal the sanctions to the World Court, is that an acceptance that means they can't object to the enforcement, can't treat enforcement as an act of war? Can a fuckin worms. I know that the orders of the Security Council aren't necessarily any more legal than a law passed by Congress - - both can be over-ruled by the courts. But North Korea doesn't look like it wants to go to court under any circumstances.
If I were in charge of the U.S. empire right now, I'd be a bit leary of enforcing any sanctions in view of the latest declaration of North Korea - - wouldn't want a new Korean War on my hands, not at this point in time. Even if they could afford to get bogged down in another quagmire, it would really leave them exposed to anyone else who wants a shot at the empire anywhere, at any point.