We’re already at war (still). Doesn’t firing ballistic missiles into or over the territory of one of our allies constitute an act of war? How about threatening to nuke us? If anything, NK has violated the armistice and we should already be in a hot war with them again.
And setting off a large nuclear explosion and then verbally threatening the U.S. and our allies with nuclear annihilation.
He has gone way past providing a justification for preemption under international law. Way way way past that point.