More than 120 nations adopted the first international treaty banning nuclear weapons on Friday at the United Nations headquarters in New York City. The initiative—led by Austria, Brazil, Mexico, South Africa, and New Zealand—was approved by 122 votes, with only the Netherlands opposed, and Singapore abstaining. The nine countries generally recognized as possessing nuclear weapons—the U.S., Russia, Britain, China, France, India, Pakistan, North Korea, and Israel—were noticeably absent from the negotiations, as were most members of NATO.

Despite being a victim of atomic attacks in 1945, Japan also boycotted the meeting. Nevertheless, the bombings of Hiroshima and Nagasaki informed Friday’s dialogue—and the conversation thereafter. “It’s been seven decades since the world knew the power of destruction of nuclear weapons,” the president of the UN conference, Elayne Whyte Gómez, told The Guardian. The agreement, she added, “is a very clear statement that the international community wants to move to a completely different security paradigm that does not include nuclear weapons.”

Friday’s ten-page treaty is extensive in its demands, prohibiting signatories from developing, testing, manufacturing, possessing, or threatening to use nuclear weapons. Nations are also prohibited from transferring nuclear weapons to one another. Having now been approved by the UN, the treaty will be open for signatures on September 20, at which point it will need to be ratified by 50 states before entering into international law.

The major obstacle, of course, is that many prominent members of the international community—and their allies—remain vocally opposed. In a joint statement on Friday, the UN ambassadors for the U.S., Britain, and France said they had no intention of joining the treaty, arguing that it “clearly disregards the realities of the international security environment.” Of particular concern, they said, was the fact that the treaty failed to address of the growing threat of North Korea’s nuclear and missile programs. Earlier this week, North Korea claimed to have tested its first intercontinental ballistic missile, which experts say may be capable of striking Hawaii and Alaska. The nation has also conducted five nuclear tests since 2006—and could be preparing for its sixth.

Rather than ban nuclear weapons and risk vulnerability to a North Korean attack, the U.S., Britain, and France hope to strengthen the Nuclear Nonproliferation Treaty (NPT), which provides nations other than the five original nuclear powers—the U.S., Russia, Britain, France, and China—from pursuing nuclear programs. In exchange, the five powers have pledged to make steps toward nuclear disarmament and give non-nuclear states access to nuclear technology for producing energy.

But many nations have criticized the NPT for failing to elicit a speedy disarmament. At the very least, Friday’s treaty introduces the concept of a nuclear-free world, and could even put pressure on nuclear powers to adopt a new set of standards. “The key thing is that it changes the legal landscape,” Richard Moyes, the managing director of Article 36, a U.K.-based organization that aims to prevent harm caused by nuclear weapons, told Agence France-Presse. As Moyes sees it, the newly-approved treaty “stops states with nuclear weapons from being able to hide behind the idea that they are not illegal.”