Snapback sanctions, the 2015 Iran nuclear deal’s fail-safe mechanism, may be back on the West’s agenda after recent threats and aggression by the Islamic Republic.

U.K. Foreign Secretary David Lammy is prepared to trigger snapback sanctions as Iran gets closer to nuclear breakout, The Telegraph reported over the weekend, citing a Foreign Office official who said that London is “committed to preventing Iran from developing nuclear weapons using every diplomatic tool available, including the snapback mechanism if necessary.”

The report comes in the immediate aftermath of Iranian Supreme Leader Ali Khamenei’s top foreign policy advisor, Kamal Kharrazi, saying that Tehran has “the technical capabilities necessary to produce nuclear weapons” and would do so if facing an existential threat.

In the past year, Iran has twice directly attacked Israel with missiles, in addition to sponsoring Hamas and Hezbollah, which have been at war with Israel for the past year, as well as the Houthis in Yemen, who have sporadically attacked Israel in addition to disrupting global commerce by attacking ships in the Red Sea. 

In addition, Iran has sold ballistic missiles and drones to Russia for use in its war against Ukraine, leading the EU and U.K. to impose sanctions last month on Iranian airlines as well as arms procurement and production firms and individuals involved in Iran’s arms industry and the Islamic Revolutionary Guard Corps.

Deployment of the snapback mechanism means that the sanctions regime of the Iran deal, known as the Joint Comprehensive Plan of Action (JCPOA), would revert to its original state.

The JCPOA included “sunset clauses,” by which sanctions on Iran would gradually expire; all sanctions would return if snapback is invoked. 

In 2020, the U.N. arms embargo on Iran ended — though the U.S., EU and U.K. kept their respective embargoes in place — and some U.N.-backed visa bans were lifted. In 2023, the sun set on U.S., EU and U.K. sanctions on some entities linked to proliferation, a U.N.-sponsored ban on importing and exporting missile equipment and technology, as well as U.N.-backed asset freezes. The U.N. ban on Iranian ballistic missile launches also expired in October 2023, and Tehran attacked Israel with ballistic missiles less than six months later. In July of this year, some limits on advanced centrifuge restrictions were lifted.

The next sunset goes into effect at the end of 2025, when past U.N. Security Council resolutions regarding the Iranian nuclear program expire, as does the snapback mechanism itself. If Lammy or any other remaining parties to the JCPOA seek snapback sanctions, they would have to take action by next fall to allow the process to play out. 

Germany or France, which together with the U.K. make up the E3, are the other likely candidates, but Russia or China are also parties to the deal. The Trump administration left the JCPOA in 2018, but attempted to trigger snapback sanctions in 2020, arguing that it could do so since the mechanism was instituted as part of the U.N. Security Council imposing sanctions on Iran, it was separate from the deal; however, the rest of the council overruled Washington.

Snapback sanctions can be implemented in response to Iran violating the JCPOA, which it has been doing since 2020, when it began enriching uranium to over 3.67%, stockpiling over 300 kilograms of low-enriched uranium and blocking International Atomic Energy Agency inspectors’ visits, among other violations. The E3 invoked the JCPOA dispute mechanism, the first step towards triggering snapback sanctions, in 2020, but did not complete the process at the U.N. Security Council.

Since then, Iran has enriched uranium up to 60% purity, according to the IAEA, bringing it to as little as one week away from reaching the 90% necessary for a nuclear bomb. After that stage, known as breakout, Iran would have to weaponize the uranium, which Israeli government sources have told Jewish Insider they believe Tehran already knows how to do.

Though Iran is at such an advanced state in the development of a nuclear weapon, Rich Goldberg, a senior advisor to the Foundation for Defense of Democracies, said it is not too late for snapback sanctions to be effective.

“It’s the primary tool of diplomatic pressure available to us, which carries a potentially powerful economic impact as well,” he said. “Why would we not want the international arms and missile embargoes to come back into force when Iran transfers drones and missiles to Russia for use against Ukraine? Why would we not want to remove all nuclear sunsets given Iran’s nuclear misconduct?”

In addition, Goldberg said that “Tehran has made perfectly clear it’s afraid of snapback for some reason. That tells me we need to trigger it immediately.”

Though the snapback mechanism is veto-proof in the U.N. Security Council, Russia and China could potentially render the sanctions ineffective by continuing to trade with Iran. They have deepened their ties with Iran, buying oil, weapons and more. Moscow and Tehran announced a defense pact last week.

Still, Goldberg said that “what matters is that we can add one more tool of political pressure on our top adversaries.”

Raz Zimmt, a researcher at the Institute for National Security Studies at Tel Aviv University, said that snapback is only a “symbolic step,” noting that the U.S. and EU never lifted their sanctions on Iran and that China doesn’t abide by them anyway.

“It sends a message to the Iranians if you have U.N. Security Council sanctions, but in practicality, it doesn’t have much significance … I’m not convinced it will make a difference,” he said.

Zimmt suggested that the best way for the West to have economic leverage on Iran is to actually enforce its sanctions, especially on Iranian oil sales to China, which is something that can be done without snapping back sanctions.

Zimmt was skeptical that the U.K. would actually invoke snapback anytime soon, noting that Iranian officials are “constantly bringing up the option of renewing their nuclear doctrine” to include the development of weapons, and that the E3 would be unlikely to take any big steps before knowing who is elected president of the U.S. and what his or her Iran policies will be.

Rather, he posited that snapback will be used as leverage by the Europeans next summer, in the months before the mechanism’s sunset, to try to get Iran to roll back its nuclear program, and in response, Iran will try to draw out negotiations until snapback expires.

Goldberg, however, said the E3 must act immediately, highlighting that the U.K. Foreign Office said it would use them “if necessary.” 

“What exactly does ‘if necessary’ even mean at this point when snapback was about JCPOA compliance?” he asked. “JCPOA is dead and buried … What exactly is London waiting for, a detonation? Because if it’s 90% enrichment they’re waiting for, I’m sorry to be the bearer of bad news: Iran has already proven they have crossed that technical threshold even if production has not started.” 

“The ball game is weaponization now — we need every stick we can find, including snapback, and we need them now,” Goldberg added.