Executive Summary: The “snapback” mechanism allows any participant in the Iran nuclear deal (JCPOA) to reimpose the UN sanctions that the deal had lifted. That mechanism will expire on October 18, 2025. The E3 (France, Germany, and the United Kingdom) intend to trigger snapback to reimpose the sanctions by the end of this week due to Iran’s continued violations of its commitments. While the move carries a limited practical effect, it formally ends the JCPOA and risks provoking an Iranian overreaction, including a potential withdrawal from the Nuclear Non-Proliferation Treaty (NPT).
What is the Iran “Snapback”?
In 2015, the United Nations Security Council (UNSC) passed United Nations Security Council Resolution (UNSCR) 2231, which endorsed the Joint Comprehensive Plan of Action (JCPOA), also known as the Iran nuclear deal. Within UNSCR 2231, there is a mechanism that allows any “individual participant within the JCPOA” to reimpose the sanctions and Iran-related UNSCRs that were lifted as part of the deal. This mechanism, known as “snapback,” is set to expire on October 18, 2025.
Following President Trump’s decision to withdraw from the JCPOA in 2018, Iran has taken retaliatory steps and has not complied with the JCPOA and UNSCR 2231. The E3 (UK, France, and Germany) initially chose not to trigger snapback sanctions on Iran because the withdrawal from the agreement had been initiated by the United States, not by Iran. The E3 also hoped to leverage the threat of snapback sanctions to negotiate a return to compliance or a new deal. However, with the ability to reimpose these sanctions set to permanently expire soon, the E3 Foreign Ministers have announced their intention to trigger the mechanism no later than the end of August if specific conditions are not met by Iran. Those conditions reportedly include:
Return to negotiations with the United States.
Resumed cooperation with the IAEA (which was suspended following the 12-day war between Iran and Israel).
Iran accounting for its 400 kg stockpile of highly enriched uranium.
Barring any last-second, unforeseen deal, the E3’s snapback initiation seems inevitable by the end of this week.
How does snapback work?
In theory, snapback triggers three distinct actions:
Reinstates UN sanctions lifted under the JCPOA (more on this below).
Provides a legal basis for the EU and the UK to reimpose their suspended sanctions.
Allows the US to reimpose sanctions (rendered moot by the US’s withdrawal in 2018).
However, the US and European dimensions are mostly irrelevant to the current discussion. The US unilaterally reinstated its sanctions following the Trump Administration’s withdrawal from the JCPOA in 2018, and has added many more sanctions since. Relief from European nuclear-related sanctions is technically still intact, but European investment, commerce, and oil sales have all been virtually non-existent since the US’s withdrawal.
That leaves the UN sanctions and UNSCRs. Here is a summary of the most important UNSCRs:
UNSCR 1696: Calls on Iran to cease uranium enrichment.
UNSCR 1737: Establishes a UN Sanctions Committee on Iran.
UNSCR 1747: Establishes an embargo on Iranian conventional arms sales.
UNSCR 1929: Calls on Iran to end ballistic missile development and establishes a Panel of Experts to monitor implementation of sanctions on Iran’s nuclear and missile programs.
At the time of their introduction, these UNSCRs exerted significant political and economic leverage over Iran and were a notable diplomatic achievement by the Bush and Obama Administrations. Unfortunately, their reinstatement will not have the same impact. Russia and China have already stated they won’t support snapback. This means that reconstructing the Panel of Experts will be impossible, as all permanent UNSC members have a veto on the funding and staffing of such committees. Likewise, the Sanctions Committee is dependent upon full UNSC member state agreement. Pending a total change of position from Russia and China, there will be no new UN Iran sanctions and no enforcement of the newly reinstated UNSCRs. The best-case scenario is that the UN Secretariat recognizes the legitimacy of the E3’s action and puts up a new website listing the UNSCRs.
There is, however, some rhetorical utility in reversing the lapsed UN bans on Iranian conventional arms sales and missile and drone development. For example, it would be easier for the US to convince neutral third parties, such as Malaysia, to prevent the transshipment of dual-use goods and keep certain countries from buying Iranian arms. However, these actions were already illegal under US (and in some cases European) law and will still be subject primarily to US enforcement.
Why are the E3 triggering snapback now?
October 18, 2025, was always going to mark an inflection point for US and European Iran policy. Ten years following the formal adoption of the JCPOA, the date was supposed to be “Termination Day” for UNSCR 2231, effectively ending all remaining UN and EU nuclear-related sanctions on Iran and sunsetting the snapback mechanism.
This, of course, is not how things have played out. After the Trump Administration withdrew from the JCPOA and reimposed unilateral sanctions, Iran stopped implementing its obligations, and no new deal has since been reached. Consequently, Iran has not earned the various benefits intended to be part of Termination Day. The E3 therefore faced three choices: initiate snapback, seek an extension, or grant Iran a significant political concession. In this context, snapback was the most viable course, though there have been attempts as recently as this week to seek an extension.
The E3 are moving now, rather than on October 18, because the complex and regimented snapback process takes at least 30 days to complete, and they want it finalized before Russia assumes the Presidency of the UN Security Council in October.
Why is this significant?
While there is little practical value to snapback, there is significant symbolic value. Triggering snapback would mean that the JCPOA is officially over, even if functionally the deal had not been implemented since 2019.
The greatest risk is that Iran seems likely to overestimate the impact of snapback and may overreact in response. Iran has long threatened to withdraw from the Non-Proliferation Treaty (NPT) if snapback is triggered. While an actual NPT withdrawal would take a minimum of 90 days and can potentially take different forms, this is a significant step. Of the 191 NPT parties, only one state – North Korea in 2003 – has ever withdrawn, after which it resumed its nuclear weapons program and conducted six nuclear tests.
Withdrawing from the NPT would mean that Iran no longer has a legal requirement to cooperate with the International Atomic Energy Agency (IAEA). And without IAEA inspectors on the ground, the international community – outside of intelligence channels – would have no way to monitor or verify Iran’s nuclear activities. While Iran already suspended cooperation with the IAEA following the recent 12-day war, the formal withdrawal is extremely risky for all parties involved, as it would diminish policymakers’ understanding of Iran’s activities and potentially give hawks in Israel and the US an excuse to restart the conflict with Iran.
While it is also possible that Iran backs away from its NPT threat and finds some other action to take, Iranian leaders have consistently signalled that they will take retaliatory action, and there is no reason to doubt them.
What comes next?
Absent a diplomatic process, additional conflict seems likely, if not inevitable. The nuclear program, although set back, retains large quantities of highly enriched uranium and advanced centrifuges, which are now unaccounted-for, maybe permanently, without oversight by the IAEA. The risk of conflict is further heightened by domestic Iranian calls for a nuclear breakout. Meanwhile, although its missile program and support for non-state proxies are diminished, Iran continues to project power externally, threatening regional security and commercial interests.
Snapback does not mitigate any of these challenges. However, from a European perspective, snapback had to be triggered because of Iran’s escalating nuclear activities (such as enrichment and building of centrifuges) over the past six years and its inability to make a new deal with the Biden and Trump Administrations.
Policy Recommendations
In the short term, the Iran situation is likely to get worse before it gets better. However, even with snapback, diplomacy is not dead. Both snapback and hypothetical NPT withdrawal are drawn-out processes with multiple opportunities for diplomatic off-ramps. However, even if snapback is fully executed, the U.S. would be well-served to switch attention to restarting a new diplomatic approach and pushing Iran to restart cooperation with the IAEA. A resumption of the Israel-Iran war only heightens the probability of regional escalation and a covert attempt at nuclear breakout. With these considerations in mind, here are key policy recommendations for the United States:
Until snapback is finalized, remain open to a temporary snapback extension if Iran resumes cooperation with the IAEA and returns to negotiations with the United States.
Support E3 decision on snapback if Iran remains unwilling to resume cooperation with the IAEA, account for its 400 kg stockpile of highly enriched uranium, and demonstrate a commitment to restart negotiations with the United States.
If snapback happens: Urge continued US, Israeli, and Iranian adherence to the Israel-Iran ceasefire.
Remain focused on a sustainable endgame. Iran’s nuclear program – even after the 12-day war – remains a significant threat. The only sustainable solution to the Iranian nuclear challenge is a diplomatic solution that ensures the IAEA can verify strict limits on Iran’s nuclear program.
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