In case you forgot, the nonproliferation treaty states that aside from the "nuclear weapon states" (China, France, Russia, the US and the UK), no other nation state should receive, manufacture or acquire nuclear weaponry. [...] Who's disallowing them? Everyone.
Except for some countries who never signed that treaty: India, Pakistan, Israel. North Korea is also no longer a signatory (they withdrew in 2003). Shouldn't there be sanctions against the other three?
Let's not kid ourselves here: North Korea is a farce.
The best possible thing that could happen for NK and the rest of the world would be a slow transition towards democracy and a complete reconstruction of its political sphere (including eliminating all current military and political personnel, up to Un himself).
You're talking about eliminating ten million people (in the military alone). 40% of the population. Please specify which method of "elimination" you had in mind.