The decision by France, Germany and the United Kingdom on August 28 to invoke the “snapback” mechanism under the Joint Comprehensive Plan of Action (JCPOA) marks a serious escalation in the long-running nuclear standoff with Iran. By taking this step, the three European states have set in motion a 30-day process that could see the automatic reimposition of United Nations Security Council sanctions once lifted, raising the risk of deeper regional instability and further polarisation in global diplomacy.
The unravelling of the JCPOA
The Iran nuclear deal, struck in 2015 between Iran and six major powers including the E3, the United States, Russia and China, was heralded as a landmark accord to ensure the peaceful character of Tehran’s nuclear programme. The deal set stringent limits on uranium enrichment, centrifuge use and stockpile levels. It also mandated exhaustive inspections by the International Atomic Energy Agency. What Iran got in return was relief from years of punishing sanctions.
However, the US, under President Donald Trump, withdrew from the deal in May 2018. Trump also reimposed sanctions. In response, Tehran gradually reduced compliance from 2019, exceeding limits on enrichment and centrifuge deployment, and eventually restricting the IAEA’s monitoring access.
Non-compliance and the European case for snapback
The E3 have justified their decision by pointing to Iran’s repeated and deliberate breaches. Since 2019, Tehran has accumulated enriched uranium far beyond the JCPOA ceiling. The IAEA reported in May that Iran held over 408kg of uranium enriched up to 60 per cent purity. While short of the 90 per cent level typically described as weapons-grade, the material is close enough to dramatically shorten the time needed to produce a nuclear device. The stockpile is more than 45 times the limit permitted under the deal.
Iran has also barred several experienced IAEA inspectors and dismantled most monitoring equipment since 2022, making verification of declared sites and stockpiles impossible. More seriously, according to European governments, the agency can no longer account for more than nine Significant Quantities (approximate amount of material that could be used to construct a nuclear explosive device) of highly enriched uranium. With no civilian justification for such holdings, the E3 argue that Iran presents a “clear threat to international peace and security.”
Europe insists it explored every diplomatic avenue before acting. The JCPOA’s Dispute Resolution Mechanism was activated, and from April 2021 to February 2022, the parties engaged in intensive negotiations to restore compliance and enable a US return. The European Union, acting as coordinator, tabled compromise texts in 2022, which Iran rejected while introducing demands seen as extraneous. In July 2025, the E3 even offered to extend the lifespan of Resolution 2231 beyond its October expiry, provided Tehran resumed talks, complied with IAEA obligations and reduced its enriched uranium stockpile. Officials now say Iran made “no substantive effort” to respond, leaving Europe with no alternative.
How snapback works
The snapback mechanism was written into the JCPOA to provide an automatic safeguard against Iranian violations. Any signatory may notify the Security Council of significant non-performance by Iran. This initiates a 30-day period during which the Council must vote on a resolution to continue sanctions relief. Such a resolution is almost certain to fail, since the E3 or the US could veto it. If no resolution is adopted, all sanctions that had been lifted are automatically reimposed.
Crucially, the procedure is veto-proof: Russia and China, although supportive of Iran, cannot block the outcome. What is restored are not new restrictions but the older resolutions dating from 2006 to 2010. These include a ban on uranium enrichment and reprocessing, an arms embargo, prohibitions on ballistic missile activities, a freeze on assets of designated individuals and entities, and inspection rights over Iranian air and maritime cargoes.
The Europeans were also working against time. The snapback clause expires on October 18, ten years after the agreement took effect. After that date, reimposing sanctions would require fresh Security Council action, subject to Russian and Chinese vetoes. Triggering the process while South Korea holds the Council presidency in September also prevents Moscow from using procedural manoeuvres once it assumes the presidency in October.
Sanctions to return
Once reinstated, the sanctions will again become binding on all countries, including Russia and China. Measures already imposed unilaterally by the US and Europe will thus be reinforced with universal legal weight. Washington, as a permanent Council member, will also gain a veto over any future attempt to lift them, giving it significant leverage.
The restored embargo will target Iranian arms sales, missile programmes and nuclear-related technology, while restricting the travel and assets of dozens of officials. The broader impact will be to deepen Iran’s economic isolation and complicate its international trade.
Iran’s rejection and possible retaliation
Tehran has condemned the European move as unlawful, insisting the E3 have no standing to invoke snapback since the United States abandoned the JCPOA first. Foreign Minister Abbas Araghchi described the step as a “provocative and unnecessary escalation” and warned that it would seriously undermine Iran’s cooperation with the IAEA. Officials maintain the nuclear programme serves only peaceful energy needs, and argue that by tearing up the deal in 2018, Washington forfeited the moral and legal basis to demand compliance.
Iran’s leaders have hinted that they could retaliate by further curtailing IAEA access or even withdrawing from the Treaty on the Non-Proliferation of Nuclear Weapons, a step that would mark a major rupture in global non-proliferation norms. There are also fears that Tehran may increase the pace of enrichment or disperse stockpiles to undisclosed sites, citing the risk of Israeli or American strikes.
Broader strategic implications
For years, Britain, France and Germany were seen as moderating influences, resisting US calls for maximum pressure. Since Trump’s return to the White House in January, however, Europe has edged closer to Washington’s position. This reflects frustration with Iran’s role in supplying drones to Russia for the war in Ukraine and a desire to maintain transatlantic unity at a time of heightened tensions.
Analysts caution that diplomacy will now be harder, not easier. Iranian officials and much of the public believe negotiations were always a pretext, and that Israel would strike regardless of concessions. The prospect of renewed violence cannot be excluded, particularly after recent Israeli raids on Iranian facilities. Snapback may thus entrench positions rather than open a path to compromise.
The diplomatic window
European leaders, the United States and the UN Secretary-General have all stressed that diplomacy remains possible. The 30-day window before sanctions automatically return is being described as a final chance for dialogue. The UN General Assembly in September may provide an opportunity for fresh talks.
Whether Iran seizes this opening is uncertain. Its leaders view the JCPOA as fatally undermined by Washington’s withdrawal, and they remain suspicious of Western intentions. Without a new framework or significant concessions on both sides, the crisis is likely to persist well beyond October.