Over 120 countries adopted the United Nations’ first-ever global ban on nuclear weapons Friday, in a significant milestone in the push against nuclear proliferation. Except for one thing: None of the countries that actually have nuclear weapons adopted the treaty, so it doesn’t technically apply to them.

The ban, formally known as the Treaty on the Prohibition of Nuclear Weapons, was officially adopted after months of negotiations by the U.N. General Assembly, with the Friday vote: 122 countries voted yes; one — the Netherlands — voted no; and one — Singapore — abstained. Among those voting yes was Iran, which reached a historic diplomatic accord in 2015 with the U.S. and five other world powers curbing Tehran’s ability to acquire a nuclear weapon.

The treaty explicitly says countries cannot “develop, test, produce, manufacture, otherwise acquire, possess, or stockpile nuclear weapons or other nuclear explosive devices.”

Yet every one of the nine countries that have nuclear weapons — the United States, Russia, Britain, China, France, India, Pakistan, North Korea, and Israel — boycotted the talks.

“To ban nuclear weapons now would make us and our allies more vulnerable, and would strengthen bad actors like North Korea and Iran who would not abide by it,” Nikki Haley, the U.S. ambassador to the U.N., told reporters at the outset of negotiations for the treaty in March.

“There is nothing I want more for my family than a world with no nuclear weapons. But we have to be realistic,” Haley said.

Still, the treaty serves as a symbolic and legal marker against using nuclear weapons in international warfare, Elayne Whyte Gomez, Costa Rica’s ambassador to the U.N. and president of the conference that negotiated the ban told reporters Thursday.

“The world has been waiting for this legal norm for 70 years,” said Whyte Gomez, referring to the nuclear bombs the U.S. dropped on Hiroshima and Nagasaki in 1945 during World War II.