On August 28, the three European participants in the Iran nuclear deal initiated a process to snap back into place U.N. sanctions that had been relieved or reformulated as part of U.N. Security Council Resolution 2231 that endorsed and implemented the deal in 2015. This Q&A, featuring Kelsey Davenport, the Director for Nonproliferation Policy at the Arms Control Association, explains what that means, what might come next, and why it matters.

Q. The U.N. Security Council passed Resolution 2231 immediately after the signing of the Joint Comprehensive Plan of Action (JCPOA) in 2015 to endorse the JCPOA and provide for its implementation. Among other things, it suspended some restrictions on Iran’s nuclear program while reformulating others, created an innovative “procurement channel” for approval of any transfers of potentially nuclear-related goods into Iran, established a first-of-its-kind “snap back” mechanism that would allow the previous U.N. sanctions architecture to be reconstituted if there were significant and unresolved non-compliance with the terms of the JCPOA, and provided for “termination” of the Security Council’s restrictions on Iran a decade after the JCPOA went into effect (unless “snap back” had occurred before that time). Before we get to the “snap back” part of the resolution, can you walk us through what you consider to be the most important features of Resolution 2231 are and why we’re hearing about them today?

Kelsey Davenport: Between 2006 and 2010, the UN Security Council passed a series of resolutions sanctioning Iran and limiting the country’s nuclear program after the International Atomic Energy Agency’s Board of Governors reported Iran to the Security Council for noncompliance with its legally required safeguards agreement.

Resolution 2231, which endorsed the 2015 nuclear deal, modified the UN sanctions and restrictions on Iran’s nuclear program and was integral to the implementation of the JCPOA. It immediately lifted sanctions and designations related to some of the country’s nuclear activities and removed or modified restrictions on the nuclear program, such as the prohibition on enrichment, necessary for JCPOA implementation. Other sanctions remained fully in place but were time-limited by the Resolution—the UN’s arms embargo remained in place for five years, and restrictions on Iran’s transfer of ballistic missiles remained in place for eight.

Furthermore, Resolution 2231 set up a unique review process for monitoring Iran’s purchase of certain materials that could be relevant to its nuclear program. Any state seeking to sell or transfer any of those materials to Iran had to seek approval from a Security Council body prior to the transfer, on which the United States (and other JCPOA participants) had a veto. This mechanism was known as the procurement channel.

Resolution 2231 contained a number of binding obligations on all UN member states. For example, the prohibition on providing nuclear or dual-use goods and services to Iran except through the procurement channel applies to all states. (The arms and missile restrictions were also universal until their expiration.).

Finally, Resolution 2231 contains what is essentially an expiration date. Ten years following the JCPOA’s adoption, on what is called “Termination Day” in the JCPOA, the Resolution provides that “all provisions of this resolution shall be terminated, and none of the previous resolutions” the Security Council had adopted to address Iran’s nuclear program will continue. On that date, “the Security Council will have concluded its consideration of the Iranian nuclear issue, and the item ‘Non-proliferation’ will be removed from the list of matters of which the Council is seized,” effectively closing the books on the Security Council’s engagement with Iran’s nuclear program. Closure of the nuclear file at the UN is particularly important to Iran, as Tehran wants to be perceived as a “normal” NPT member state. Termination Day is October 18 of this year – and if Resolution 2231 expires, the snap back provisions that could be used to put multilateral sanctions on Iran’s nuclear program back in place would expire along with it.

Q. Turning to that snap back mechanism, how does it work and who can trigger it?

KD: Snapback is a unique mechanism that allows any participant in the nuclear deal that is also a member state (that is, all but the EU) to reimpose the UN sanctions and restrictions on Iran that were removed or modified by Resolution 2231 using a process that cannot be blocked. It was included in Resolution 2231 because members of the P5+1 group (China, France, Germany, Russia, the United Kingdom, and the United States) were concerned that if Iran violated the nuclear provisions of the JCPOA, under normal Security Council procedures, any one of the P5 states could veto the adoption of new, binding Security Council sanctions. The snapback mechanism ensured that, through October 2025, there was a veto-proof path to restoring the significant multilateral restrictions on Iran’s nuclear program that had been in place prior to the JCPOA.

To trigger the snapback mechanism, any participant in the JCPOA that is a UN member state (that is, the P5+1) can notify the Security Council of an issue that “constitutes significant nonperformance of commitments” in the nuclear deal. The President of the Security Council must then submit a draft resolution calling for the continuation of UN sanctions relief specified by the JCPOA within 10 days of the notification. The Security Council then has 30 days to vote on the resolution. If that resolution passes, the previous sanctions are not restored (i.e., they do not “snap back”). However, the participant that triggered the snapback could veto the resolution calling for the continuation of sanctions relief if its concerns had not been resolved, snapping back the previous sanctions and restrictions.

The United States, having withdrawn from the JCPOA in May 2018, cannot trigger snapback. The Trump administration attempted to use the snapback mechanism to prevent the UN arms embargo on Iran from expiring in 2020, but the Security Council president said that the United States could not do so because it was no longer a “participant” to the nuclear deal.

Q. On August 28th, the “E3” (France, the United Kingdom, and Germany) sent a letter to the President of the Security Council invoking snap back in an attempt to pressure Iran to make concessions regarding its nuclear program. It had previously been reported that JCPOA participants were in discussions about an extension of the termination provisions, which would have bought more time before there was a need to come to a decision on pulling the snap back trigger. What does it mean in practice that the E3 have initiated snap back? Was doing so at this stage wise?

KD: The E3 was in a tough position. Iran’s violations of the JCPOA since 2019 brought the country technically to the threshold of nuclear weapons and, after the U.S. and Israeli strikes in June, Iran had suspended cooperation with the International Atomic Energy Agency (IAEA), violating its legally binding safeguards obligations and removing all oversight of its nuclear activities. Furthermore, Russia and China’s failure to condemn Iran’s safeguards violations raised legitimate concerns about whether the Security Council would vote to sanction or condemn Iran in the future for safeguards noncompliance. So if the E3 did not initiate snapback, the mechanism would expire and it would be unlikely, barring any clear move by Iran to weaponize, that the Security Council would put any new pressure on Iran.

On the other hand, pressure works best when paired with a credible, diplomatic off-ramp. Currently, it is not clear that the United States perceives negotiations as an urgent necessity or that Iran views the United States as a credible negotiating partner, despite continued expressions of support for a deal.

Furthermore, Iran does not want to be perceived as capitulating to pressure, so initiating snapback will likely provoke an Iranian response, such as its threat to withdraw from the Nuclear Nonproliferation Treaty (NPT). As a result, snapback could further escalate tensions and put the United States and Iran back on the path to conflict.

By initiating snapback, the E3 has set a 30 day deadline for reaching an agreement that staves off snapback taking effect. This could inject much-needed urgency into the talks if both sides are willing to engage, but there are still significant challenges. Ideally, the E3 will work with the United States on a limited deal that extends snapback in exchange for Iran taking steps to reduce nuclear risk. The E3 suggested this in an Aug. 28 statement, saying “[w]e will use the 30-day period to continue to engage with Iran on our extension offer, or on any serious diplomatic efforts to restore Iran’s compliance with its commitments.”

Fully restoring Iran’s compliance with the JCPOA in the next 30 days is unrealistic, particularly due to the verification challenges that stem from the strikes on Iran’s nuclear facilities, but the E3 suggested they would accept less. In an Aug. 8 letter, the E3 said it would extend snapback for six months in exchange for resuming negotiations and “addressing some of the international community’s most immediate concerns regarding the transparency” of its nuclear program.

Q. Iran has, as expected, condemned the “illegal and unfounded” E3 action. And for its part, the U.S. State Department issued a press statement that “[o]ver the coming weeks, we will work with [the E3] and other Members of the UN Security Council to successfully complete the snapback of international sanctions and restrictions on Iran…” On one hand, the United States is an essential player in getting negotiations back on track if it’s even viable to do so. But after joining Israel’s bombing campaign and striking Iran’s nuclear program earlier this summer, its credibility is badly damaged. Assuming U.S. President Donald Trump still wants a deal (perhaps a big assumption at this stage), if there is a path for diplomacy that could avert snap back coming into effect, what does that look like?

KD: Iranian Foreign Minister Abbas Araghchi said that Iran is still interested in “fair and balanced” negotiations over its nuclear program. But to resume talks, Araghchi said that Iran is looking for assurances that its nuclear rights under the Nuclear Nonproliferation Treaty will be respected and there will be no military aggression against Iran while negotiations are ongoing.

To address Iran’s concerns and the proliferation risks identified by the E3 in their Aug. 28 statement on snapback, the United States and Iran could negotiate an interim arrangement. The arrangement could include a commitment from Iran to allow IAEA inspectors back into all nuclear facilities and cooperation on accounting for its stockpiles of 60 percent enriched uranium, which remain unknown after the Israeli and U.S. bombings in June. An interim arrangement could also recognize Iran’s rights to a peaceful nuclear program under the Nuclear Nonproliferation Treaty.

In exchange, the United States could also work with E3, Russia, and China on a UN Security Council resolution to extend the snapback mechanism for six months. The resolution could also encourage all states to support the negotiation of a comprehensive agreement. To be a more credible player in this process, the United States would likely need to commit to refrain from military action against Iran or supporting military action by any other state. Any further strikes on Iran would likely be unlawful and although the Trump administration may be loath to give up the threat to military force, Trump no longer views Iran’s nuclear program as an imminent threat and wants to avoid a broader U.S.-Iran conflict. Therefore, committing to forgo military action for six months would solidify and strengthen the ceasefire agreement that President Donald Trump announced in June without undermining U.S. security, reduce tensions, and buy time for negotiations on a comprehensive agreement.

Q. If diplomacy does not succeed in this compressed timeframe and sanctions snap back is completed next month, what would the U.N. sanctions architecture on Iran’s nuclear program look like? And for the rest of the world, what activity that’s currently permitted under UNSCR 2231 would be prohibited?

KD: The reimposition of UN sanctions on Iran will have little economic impact, but alongside other types of impacts, it would mark an official end of the JCPOA era. That’s because the pre-JCPOA UN Security Council posture would be reinstated, and without the significant reformulations, carve-outs, and other innovative mechanisms in Resolution 2231, implementation of many of the JCPOA’s provisions becomes impossible.

On economic impacts, when Trump withdrew from the JCPOA in May 2018, despite Iran’s compliance with the accord, and reimposed U.S. sanctions, the breadth of those measures ended nearly all of the economic engagement with Iran that was permitted under the JCPOA. The reimposition of the arms embargo and the prohibitions on the import and export of ballistic missiles and drones, however, will make certain transactions, such as Iran’s provision of drones to Russia, illegal.

More directly relevant to Iran’s nuclear program are the UN provisions regarding the country’s nuclear activities. Snapback will restore prohibitions on Iran’s nuclear activities that Tehran views as infringing on its nuclear rights under the NPT, including the binding requirement on Iran to suspend uranium enrichment and prohibit any work on heavy-water reactors. It also prohibits plutonium reprocessing and investment in nuclear activities overseas. Additionally, it will restore the prohibition on any activities relevant to ballistic missile development.

In addition to implementing the sanctions, all UN member states will be prohibited from providing any materials or equipment to Iran that could be used for its nuclear and/or missile programs and providing finances, training, or resources that would be relevant to advancing the nuclear program.

Q. Sanctions enforcement is often less of an uphill battle when there is alignment among key stakeholders (including countries that want to trade with Iran) on the goals of the sanctions and when there is a diplomatic process in place that has a realistic prospect of achieving them. Do you think there is any agreement on goals for Iran’s nuclear program, or any prospect of a viable diplomatic process going forward? If not, do you foresee difficulty getting states to comply with the U.N. sanctions regime?

KD: There is broad agreement that Iran should remain a non-nuclear weapon state and party to the NPT, but significant disagreements between key states over the strategies to prevent a nuclear armed Iran, the role that sanctions should play, and who is to blame for the current crisis.

Russia and China, for instance, oppose the snapping back of UN sanctions. There is a real risk that neither country will enforce the reimposed UN measures, despite being legally obligated to do so, if snap back becomes effective after 30 days. Snapping back sanctions after Israel and the United States struck Iran before diplomacy was exhausted risks additional states viewing the reimposition as unjust and a further example of nuclear weapon states undermining the NPT’s guarantee that states can pursue peaceful nuclear programs.

The Security Council has little leverage to compel states to implement resolutions, including those that are legally binding. It essentially relies on member states to do so. So there is a real possibility that the E3’s attempt to build leverage backfires by pushing states to ignore the Security Council’s provisions and driving Iran to retaliate.

Q. What are the best and worst case scenarios that we could see over the next few months?

KD:In the best case scenario, the E3 and the United States have a plan for a quick, pragmatic negotiation with Iran that extends the snapback mechanism, restores transparency on Iran’s nuclear program, addresses Iran’s concerns about the security of its nuclear facilities, and sets the table for further diplomacy.

In the worst case, Iran responds to snapback by withdrawing from the NPT and either overtly or more likely covertly, embarks on a path toward weaponization. In this scenario, it is highly likely that conflict between Iran, Israel and the United States re-erupts.

FEATURED IMAGE: (L-R) French President Emmanuel Macron, Germany’s Chancellor Friedrich Merz and British Prime Minister Keir Starmer pose for the media at a hotel prior to an E3 meeting on the sidelines of the 2025 NATO summit on June 24, 2025 in The Hague, Netherlands. (Photo by Ben Stansall – WPA Pool/Getty Images)