The United Nations Security Council on Saturday evening reimposed broad sanctions and restrictions on Iran, after determining that Tehran had engaged in “significant non-performance” of its nuclear obligations.

The sanctions were restored under the snapback provision of UN Security Council Resolution 2231, which endorsed the 2015 Joint Comprehensive Plan of Action (JCPOA). That mechanism allowed for the automatic reimposition of earlier sanctions if Iran was found to be in noncompliance, and it was deliberately structured to prevent a veto by permanent Council members. Under the terms of the resolution, once a JCPOA participant notified the Council of violations, the suspended measures would resume after 30 days unless the Council voted to extend relief.

The decision followed a failed round of eleventh-hour diplomacy during the UN Security Council Meeting, where Iran Foreign Minister Seyed Abbas Araghchi sought to forestall sanctions by offering inspectors limited access to enrichment sites. European leaders, however, insisted on broader conditions: full access for the International Atomic Energy Agency (IAEA), disclosure of Iran’s 400-kilogram stockpile of highly enriched uranium, and direct negotiations with Washington.

The move marked the conclusion of the so-called snapback mechanism—a clause of the 2015 JCPOA—invoked by France, Britain, and Germany on August 28. The revived resolutions (1696, 1737, 1747, 1803, 1835, and 1929) collectively ban uranium enrichment, restrict ballistic missile activities, reinstate an arms embargo, and impose travel bans and asset freezes on dozens of Iranian individuals and entities. They also authorize states to seize prohibited cargo transferred by Iran, including conventional arms.

US Secretary of State Marco Rubio welcomed the snapback, saying: “The world will not acquiesce to threats and half measures—and Tehran will be held to account.”

Iran denounced the sanctions as “illegal, void, and no standing.” Iran argued that the United States’ withdrawal from the nuclear accord in 2018 nullified the agreement, making it unlawful for European states to invoke its provisions. In remarks in New York, Iran Foreign Minister Seyed Abbas Araghchi reminded reporters about Iran’s recent agreement to cooperate with the IAEA and that “diplomacy would never die but it would be certainly more difficult and more complicated than before.” Iran also passed a law in July suspending cooperation with the IAEA.

Implementation of the restored measures is expected to vary across states. While European powers have already indicated they will comply, Russia and China have stated that they do not recognize the legitimacy of the snapback and will continue trade with Iran, particularly in the energy and defense sectors.