The UN needs to make a declaration of condemnation of their previous tests and emphasize that they were illegal and that any new attempts will hold severe consequences.
Then, if they do perform another launch, WE need to destroy that rocket, and one of our major allies needs to destroy the pad and base it came from.
And then within hours, the command arm may get a nasty package delivery as well, unless they fully surrender and give up all this hate mongering crap.
Their people need food and an economy and a spot on the national table, not be starved and murdered by a bastard dictator in a communist regime.
And yes, it IS up to us to stop it.