On July 20, 2015, the UN Security Council adopted Resolution 2231 (2015) to implement the Joint Comprehensive Plan of Action (JCPOA) and other provisions concerning Iran's nuclear program, Tehran's development of missiles, and arms transfers to and from Iran. In August 2020, the United States invoked the resolution's "snapback" mechanism, which required the Security Council to reimpose UN sanctions lifted pursuant to Resolution 2231 and the JCPOA. (CRS Report R40094, Iran's Nuclear Program: Tehran's Compliance with International Obligations.) Although that effort failed (see below), France, Germany, and the United Kingdom (UK), collectively known as the "E3," invoked the snapback mechanism on August 28, 2025, resulting in the sanctions' reimposition on September 27, 2025.
Resolution 2231 stipulated that the council, "seized of the Iranian nuclear issue" since 2006, was to end its consideration of the matter on October 18, 2025. The resolution's snapback mechanism then would have ceased to operate. The JCPOA has effectively expired; snapback reimposed previously terminated UN sanctions and indefinitely extended both the sanctions and Iran's nuclear program as a subject of Security Council consideration.
Prior to June 2025 U.S.-Israeli airstrikes on Iranian nuclear facilities, including those associated with Tehran's enrichment program, Tehran's expansion of that program had decreased the amount of time necessary for Iran to produce enough fissile material for use in a nuclear weapon. (CRS In Focus IF12106, Iran and Nuclear Weapons Production.) The International Atomic Energy Agency (IAEA) withdrew inspectors from Iran after the strikes.
The extent to which the June 2025 strikes impacted Iran's enrichment program is unclear; the IAEA has not been able to inspect the attacked Iranian nuclear facilities. Whether and to what extent subsequent U.S.-Israeli strikes, which began on February 28, affected this program is unclear. A June 2026 memorandum of understanding (MOU) commits the United States and Iran to "negotiating and achieving" a deal governing a range of issues, including Iran's nuclear program and U.S. and UN sanctions, within a "maximum [of] 60 days extendable with mutual consent." The MOU is silent on the future of IAEA safeguards in Iran.
The JCPOA, finalized in July 2015 by Iran and China, France, Russia, the UK, the United States, and Germany (collectively known as the "P5+1"), required Iran to implement constraints on its uranium enrichment and heavy water nuclear reactor programs, as well as allow the IAEA to monitor Tehran's compliance with the agreement. These programs have caused international concern because they could produce fissile material for use in nuclear weapons.
Prior to the JCPOA, Iran was improving its ability to produce such fissile material, despite what U.S. officials characterized as UN and other sanctions' apparent success in slowing Tehran's nuclear program. At the time, IAEA and U.S. officials observed that IAEA safeguards on Iran's declared nuclear facilities likely would have detected an Iranian attempt to use them for producing nuclear weapons. (CRS Report R43333, Iran Nuclear Agreement and U.S. Exit.)
Pursuant to the JCPOA, Tehran received relief from sanctions imposed by the European Union, United Nations, and United States. On January 16, 2016, the agreement's Implementation Day, the Security Council terminated the provisions of seven resolutions: 1696 (2006), 1737 (2006), 1747 (2007), 1803 (2008), 1835 (2008), 1929 (2010), and 2224 (2015). The first six of these resolutions required Iran to take several steps, such as cooperating fully with an IAEA investigation of Tehran's nuclear activities as well as suspending sensitive nuclear activities. These resolutions also contained sanctions on Iran. In May 2018, President Donald J. Trump issued a memorandum stating that the United States would no longer participate in the JCPOA and would reimpose sanctions that had been suspended pursuant to the agreement. Arguing that subsequent efforts by the remaining JCPOA participants, known as the "P4+1," were inadequate to sustain the agreement's benefits for Iran, Tehran undertook nuclear activities that exceeded JCPOA-mandated limits.
Beginning in July 2019, the IAEA verified that some of Iran's nuclear activities were exceeding JCPOA-mandated limits; according to agency reports, Iran's government subsequently increased the number of such activities. In February 2021, Iran stopped allowing the IAEA "to conduct verification and monitoring activities in relation to the JCPOA," according to a February 27, 2026, report from IAEA Director General Rafael Grossi. Iran's JCPOA commitments supplement Tehran's obligations pursuant to its IAEA comprehensive safeguards agreement and the nuclear Nonproliferation Treaty (NPT). (CRS Report R40094, Iran's Nuclear Program: Tehran's Compliance with International Obligations.)
The NPT, which Iran ratified in 1970, prohibits Iran from obtaining or producing nuclear weapons. The treaty also requires countries such as Iran to conclude a comprehensive IAEA safeguards agreement. Such agreements empower the agency to detect the diversion of nuclear material from declared nuclear facilities and to detect undeclared nuclear activities and material.
In February 2021, Iran ceased implementing the Additional Protocol to its comprehensive safeguards agreement. Such protocols provide the IAEA with additional authority to inspect certain nuclear-related facilities and demand information from member states. Iran had been implementing provisionally its additional protocol pursuant to the JCPOA, which also required Tehran to seek the Iranian parliament's ratification of the protocol no later than October 2023. Iran had signed such an additional protocol in late 2003 but stopped implementing it in early 2006.
In February 2026, the IAEA last apparently reported on the agency's JCPOA-mandated monitoring of Iranian compliance with agreement-specific restrictions. The IAEA currently monitors Iranian compliance with the Security Council resolutions adopted between 2006 and 2010 and a November 20, 2025, IAEA Board of Governors resolution.
In addition to the JCPOA-related provisions, Resolution 2231 (2015) imposes other requirements on Iran, some of which have expired. For example, the resolution restricted exports of missile-rated items to Iran until October 2023; other restrictions concerning Iranian imports and exports of conventional weapons expired in October 2020. Despite lacking a direct connection to the country's nuclear program, previous arms restrictions, the first of which were imposed by Security Council Resolution 1747 (2007), were part of a broad U.S.-led approach of pressuring Iran to comply with relevant council resolutions.
According to Resolution 2231, a JCPOA participant could, after notifying the Security Council of an issue that the government "believes constitutes significant non- performance of [JCPOA] commitments," trigger an automatic draft resolution to keep sanctions relief in effect. The United States in August 2020 initiated the snapback process, but the P4+1 governments and the Security Council president argued that the United States lacked the right to proceed with snapback because Washington had ceased participating in the JCPOA.
Despite a September 19, 2020, U.S. contention that snapback had reinstated previously terminated sanctions, UN Secretary General António Guterres wrote that the uncertainty about U.S. snapback initiation required the Secretary General to refrain from proceeding on the matter. In February 2021, the Biden Administration reversed the U.S. position on snapback. President Trump's February 4, 2025, National Security Presidential Memorandum/NSPM-2 directed the U.S. Permanent Representative to the UN to "work with key allies to complete the snapback of international sanctions and restrictions on Iran."
The E3 invoked the snapback mechanism in an August 28, 2025, letter. The Security Council president introduced a draft resolution on September 19 that would have maintained sanctions relief. The council did not adopt the resolution. China and Russia introduced a resolution on September 26, 2025, that would have effectively extended the end of Security Council consideration of the "Iranian nuclear issue" until April 18, 2026, with "a possibility for a further extension." The council did not adopt the resolution. The conclusion of the snapback process resulted in the sanctions' reimposition on September 27, 2025. The same day, Secretary of State Marco Rubio described the E3 action as "an act of decisive global leadership."
In an October 18, 2025, letter to the Security Council, China, Iran, and Russia argued that the E3 lacks standing to invoke the snapback mechanism because the three governments had "ceased to perform" their JCPOA and Resolution 2231 commitments. The E3 failed to "exhaust the procedures" of a dispute resolution mechanism contained in the JCPOA, according to the letter, which stipulates that both Resolution 2231's provisions and the council's "consideration of the Iranian nuclear issue" have ended. The dispute concerning the resolution's status has continued in council meetings, most recently on June 9.
In addition to reimposing sanctions and other Security Council resolutions' requirements, snapback has ended the process by which the council was to have ceased in 2025 its consideration of the Iranian nuclear issue. The Security Council had adopted Resolution 2231, as well as all the resolutions that had imposed sanctions on Iran, under Chapter VII, Article 41, of the UN Charter. This provision enables the Security Council to adopt "measures not involving the use of armed force," including sanctions, "to give effect to its decisions" concerning "threats to the peace, breaches of the peace, and acts of aggression." Since adopting Resolution 1737 (2006), the council has been considering the Iranian nuclear issue pursuant to Article 41.
The November 2025 IAEA board resolution requests the IAEA Director General to report "on the implementation of Iran's NPT Safeguards Agreement," as well as the aforementioned Security Council resolutions.
Reacting to the invocation of snapback, Iranian Foreign Minister Abbas Araghchi stated on September 30, 2025, that "Iran's Supreme National Security Council will assess the situation and ultimately adopt 'the right and well-calculated decisions' in line with national interests." Iran is bound by its NPT obligations, but not by the JCPOA transparency measures governing, or physical constraints on, the government's enrichment program.
Iran has cited JCPOA Paragraph 36 as grounds for Tehran's decision to end all JCPOA-mandated transparency measures that supplement the government's IAEA safeguards agreement. The agency currently implements inspections and monitoring in Iran pursuant to Tehran's comprehensive safeguards agreement only, which is of indefinite duration; as noted, Tehran has ceased implementing the Additional Protocol to that safeguards agreement.
The June 2026 MOU states that the final negotiated agreement "will be endorsed by a binding" UN Security Council resolution but does not further specify.