North Korea is currently under international sanctions for violating several UN Security Council resolutions. That means that the majority of the UN considers North Korea's missile/nuclear program to be a problem, specifically destabilizing the region and undermining the global nonproliferation regime. 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. The NWS are also the five permanent members of the Security Council.
So within the bounds of international law and politics, North Korea is indeed disallowed to have ICBMs. Who's disallowing them? Everyone. As of the last few resolutions, even China has decided to withdraw their support, making the resolutions passed unanimously. Nuclear weapons aren't something you get to unilaterally decide you'll develop and own, and if you do, other countries will be extremely suspicious of you and for good reason.
Let's not kid ourselves here: North Korea is a farce. Its people is continuously under threat of famine, is being brainwashed, held back on just about every level, because the leadership of the country wants to conserve an iron grip on their small patch of land. As such, it's one of the poorest and most isolated places on the planet, and politically is extremely unstable and dangerous. You can't consider them on a rational level because they are not a rational actor. They have severe delusions of grandeur, regularly threaten just about every neighbor of armed conflict, often for no apparent reason, etc. 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). Failing that, I hope that one day the rest of the world decides to act upon this retarded stepchild and cut the head off - the transition would be far more traumatic, but at least it'd happen.