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Congression& Research Service
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Updated February 9, 2026


Iran's Nuclear Program and UN Sanctions Reimposition


UN  Security Council Resolution 2231 (2015), which the
council adopted on July 20, 2015, implements the Joint
Comprehensive  Plan of Action (JCPOA) and contains 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 requires the
Security Council to reimpose UN sanctions lifted pursuant
to Resolution 2231 and the JCPOA. (See CRS Report
R40094, Iran's Nuclear Program: Tehran's Compliance
with International Obligations, by Paul K. Kerr.) Although
that effort failed, France, Germany, and the United
Kingdom  (UK) (collectively known as the E3) on August
28, 2025, invoked the snapback mechanism, which resulted
in the sanctions' reimposition on September 27, 2025.
Resolution 2231 stipulates that the council, which has been
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 would then have ceased
to be operational. The 2025 invocation of snapback not only
reimposes previously terminated sanctions but also extends
them, and Iran's nuclear program as a subject of Security
Council consideration, indefinitely.

  ackground: JCPOA
The JCPOA,  finalized in July 2015 by Iran and China,
France, Germany, Russia, the United Kingdom, and the
United States (collectively known as the P5+1), requires
Iran to implement constraints on its uranium enrichment
and heavy water nuclear reactor programs, as well as allow
the International Atomic Energy Agency (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.
Pursuant to the JCPOA, Tehran received relief from
sanctions imposed by the European Union, United Nations,
and United States. On the agreement's January 16, 2016,
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). Resolutions 1737 (2006), 1747 (2007), 1803
(2008), and 1929 (2010) all imposed sanctions on Iran.
In May 2018, President Donald 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 has
undertaken some nuclear activities that exceed JCPOA-
mandated limits.


ran's   Nuclear Program and Seected
CPOA ProvsIons
Beginning in July 2019, the IAEA verified that some of
Iran's nuclear activities were exceeding JCPOA-mandated
limits; the government has since increased the number of
such activities. Tehran has also curtailed IAEA monitoring
of Iran's JCPOA commitments, which supplement Tehran's
obligations pursuant to its IAEA comprehensive safeguards
agreement and the nuclear Nonproliferation Treaty (NPT).
(See CRS Report R40094, Iran's Nuclear Program:
Tehran's Compliance with International Obligations, by
Paul K. Kerr.)
The NPT, which Iran ratified in 1970, includes prohibitions
on obtaining or producing nuclear weapons.
Comprehensive  safeguards agreements empower the
agency to detect the diversion of nuclear material from
declared nuclear facilities, as well as to detect undeclared
nuclear activities and material.
Iran also ceased implementing the Additional Protocol to its
comprehensive safeguards agreement in February 2021.
Such protocols increase the IAEA's ability to investigate
undeclared nuclear facilities and activities in nonnuclear-
weapon  states by increasing the agency's authority to
inspect certain nuclear-related facilities and demand
information from member states. Pursuant to its JCPOA
commitments, Iran is required to implement provisionally
its additional protocol; Tehran was to have sought the
Iranian parliament's ratification of the protocol no later than
October 2023. Iran originally signed such an additional
protocol in late 2003, but stopped implementing it in early
2006.
Moreover, the IAEA no longer conducts JCPOA-mandated
monitoring of Iranian compliance with agreement-specific
restrictions that supplement Iran's safeguards obligations.
Had the JCPOA  been fully implemented, most of its
nuclear-related restrictions would have expired. At that
point, Tehran's nuclear program will be governed
indefinitely by Iran's obligations pursuant to the NPT, the
government's IAEA  comprehensive safeguards agreement
and Additional Protocol, and restrictions on specific dual-
use activities, which could contribute to the development
of a nuclear explosive device.
UN   SeCUrity COUnci ReSOlUtOn 223
(2015)   and   Snapback
In addition to its JCPOA-related provisions, Resolution
2231 imposes other requirements on Iran. 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, were part of a broad U.S.-led approach of pressuring