The way I see it is they have no legal right that America must recognize and morally when someone is the biggest state sponsor of terrorism in the world and wants your country to die they have no moral right that anyone else need recognize either.
I don't think anybody believes Iran should have nukes, and it has nothing to do "legal" or moral" rights, weapons of mass destruction aren't legal or moral.
Nobody thinks North Korea should have nukes either, but oh well, it happened, so we deal with it.
I don't think there would be a way to deal with Iran if they got nukes, not for long.
Morally, nobody has a right to nuclear weapons, but we can't un-ring that bell, and as long as the technology proliferates, we can't contain it forever, just postpone it. The technical knowledge is on the internet right now, with the materials, a good reasonably good physicist can make one and I don't think we can control the requisite materials that long. We aren't that far away from a situation where a motivated terrorist can make a nuke and put it in a car trunk, shipping container, or even a suitcase.
In the long run, we are screwed.