A blockade is an act of war, in and of itself.
It might or might not head off further trouble. NK may have all it needs already to wreak all the havoc it has in mind.
So what does the ronery runt goon really want? Are any doors to better angels even left, or is raw power what he speaks? If the latter we might as well coordinate with South Korea to decapitate so as to replace with something better — in fact to unite Korea under the South government.