I think it was called the Nuclear Proliferation Treaty or something

The treaty on the non-proliferation of Nuclear Weapons was put into effect in the 70's. That treaty also calls for the cessation of the manufacture of nuclear weapons. But, since we re-initiated the process of manufacturing plutonium pits in 1997, and have been assembling new batches of nuclear weapons since 1998, it's pretty apparent that we don't hold much regard for the ideas outlined in that treaty.