A United Nations treaty banning nuclear weapons is set to go into effect in 90 days. On Saturday, Honduras became the 50th nation to ratify the Treaty on the Prohibition of Nuclear Weapons, which bans the development, testing and possession of nuclear warheads, as well as any threat to use such weapons. The treaty has not been signed by any of the world’s nine nuclear powers — Britain, China, France, India, Israel, North Korea, Pakistan, Russia and the United States.