At the United Nations headquarters in New York City, dozens of countries have signed on to a landmark treaty to ban nuclear weapons worldwide. The United Nations calls it the world’s first legally binding treaty banning nuclear weapons. It prohibits the development, testing and possession of nuclear weapons, as well as using or threatening to use these weapons. The treaty was approved by 122 U.N. member states in July, despite heavy U.S. opposition to the treaty. Following the treaty’s approval, the U.S., Britain and France published a joint statement saying they “have not taken part in the negotiation of the treaty … and do not intend to sign, ratify or ever become party to it.” The treaty will take effect 90 days after 50 U.N. member states have ratified it.