The point of the NPT, if you read it and see what it does, is the create transparency. Of course it has no teeth, for that it would need an air force to blow up anyone that develops nuclear weapons. The point is it highlights countries quickly that are not playing by the rules so other countries know who is developing what. IT IS THEN UP TO THE INTL COMMUNITY TO PUNISH NOT A PIECE OF PAPER. Therefore, it is the US fault, among others, because they have said well, 'ahhh, i guess it doesn't really matter, go ahead' ruining the whole point!
from the article: A new nuclear age