Updated September 18, 2020
Iran’s Nuclear Program and U.N. Sanctions Reimposition
U.N. Security Council Resolution 2231 (2015), which the
The NPT, which Iran ratified in 1970, includes prohibitions
council adopted on July 20, 2015, implements the Joint
on obtaining or producing nuclear weapons.
Comprehensive Plan of Action (JCPOA) and contains other
Comprehensive safeguards agreements are designed to
provisions concerning Iran’s nuclear program, Tehran’s
enable the agency to detect the diversion of nuclear material
development of missiles, and arms transfers to and from
from declared nuclear facilities, as well as to detect
Iran. The United States has threatened to invoke the
undeclared nuclear activities and material. (See CRS Report
resolution’s “snapback” mechanism, which requires the
R40094, Iran’s Nuclear Program: Tehran’s Compliance
Security Council to reimpose U.N. sanctions lifted pursuant
with International Obligations, by Paul K. Kerr.)
to Resolution 2231 and the JCPOA.
Iran is also implementing the Additional Protocol to its
The JCPOA, finalized in July 2015 by Iran and China,
comprehensive safeguards agreement. Such protocols
France, Germany, Russia, the United Kingdom, and the
increase the IAEA’s ability to investigate undeclared
United States (collectively known as the P5+1), requires
nuclear facilities and activities in nonnuclear-weapon states
Iran to implement constraints on its uranium enrichment
by increasing the agency’s authority to inspect certain
and heavy water nuclear reactor programs, as well as allow
nuclear-related facilities and demand information from
the International Atomic Energy Agency (IAEA) to monitor
member states. Pursuant to its JCPOA commitments, Iran is
Tehran’s compliance with the agreement. Prior to the
implementing provisionally its additional protocol; Tehran
JCPOA, these programs caused international concern
is to seek ratification of the protocol by the Iranian
because they could both have produced fissile material for
parliament no later than October 2023. Iran originally
use in nuclear weapons.
signed such an additional protocol in late 2003, but stopped
implementing it in early 2006.
Pursuant to the JCPOA, Tehran received relief from
sanctions imposed by the European Union, United Nations,
The IAEA also continues to monitor JCPOA restrictions,
and United States. On the agreement’s January 16, 2016,
which supplement Iran’s safeguards obligations and
Implementation Day, the Security Council terminated
prohibit Iran from engaging in a number of dual-use
sanctions imposed by three previous resolutions on Iran; the
“activities which could contribute to the development of a
council adopted the first of these resolutions (1996) in 2006
nuclear explosive device.” Should the JCPOA be
and the last (1929) in 2010. The sole operative Security
implemented as envisioned in the agreement, most of its
Council resolution concerning Iran’s nuclear program,
nuclear-related restrictions will expire. In that case,
Resolution 2231, also stipulates that the council, which has
Tehran’s nuclear program will be governed indefinitely by
been seized of the “Iranian nuclear issue” since 2006, is to
Iran’s obligations pursuant to the NPT, the government’s
end its consideration of the matter in 2025. The resolution’s
IAEA comprehensive safeguards agreement and Additional
snapback mechanism will then cease to be operational.
Protocol, and the dual-use restrictions described above.
In May 2018, President Donald Trump issued a
U.N. Security Council Resolution 2231
memorandum stating that the United States would no longer
(2015) and Snapback
participate in the JCPOA and would reimpose sanctions that
In addition to its JCPOA-related provisions, Resolution
had been suspended pursuant to the agreement. Arguing
2231 imposes other requirements on Iran. For example, the
that subsequent efforts by the remaining JCPOA
participants, known as the “P4+1,” were inadequate to
resolution prohibits certain arms transfers to Iran; bans all
sustain the agreement’s benefits for Iran, the government
Iranian exports of conventional arms until October 18,
2020; and restricts exports of missile-rated items to Iran
has undertaken some nuclear activities that exceed JCPOA-
until October 2023. Despite lacking a direct connection to
mandated limits. Iranian officials continue to assert that
the country’s nuclear program, previous arms restrictions,
Tehran will resume implementing all of its JCPOA
the first of which were imposed by Security Council
commitments if the P4+1 does so.
Resolution 1747 (2007), were part of a broad U.S.-led
Iran’s Nuclear Program and Selected
approach of pressuring Iran to comply with relevant council
JCPOA Provisions
resolutions. (For more on the arms restrictions, see CRS In
Focus IF11429, U.N. Ban on Iran Arms Transfers, by
Although some Iranian nuclear activities exceed JCPOA-
Kenneth Katzman.)
mandated limits, other aspects of the country’s nuclear
program still comply with those limits. Tehran has
According to Resolution 2231, a JCPOA participant can,
continued to allow IAEA monitoring of Iran’s JCPOA
after notifying the Security Council of an issue that the
commitments, which supplement Tehran’s obligations
government “believes constitutes significant non-
pursuant to its IAEA comprehensive safeguards agreement
performance of [JCPOA] commitments,” trigger an
and the nuclear Nonproliferation Treaty (NPT).
automatic draft resolution keeping sanctions relief in effect.
A U.S. veto of this resolution would both reimpose the
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Iran’s Nuclear Program and U.N. Sanctions Reimposition
suspended sanctions and end expiration of the conventional
force,” including sanctions, “to give effect to its decisions”
arms and missile-related export restrictions, as well as
concerning “threats to the peace, breaches of the peace, and
Security Council consideration of the Iranian nuclear issue.
acts of aggression.” Since adopting Resolution 1737 in
2006, the council has been considering the Iranian nuclear
Whether the United States has the status to invoke
issue pursuant to Article 41. Iranian officials have touted
Resolution 2231’s snapback mechanism is under debate.
the end of this status, which, as noted, Resolution 2231
The JCPOA lacks a withdrawal clause, and no Security
stipulates.
Council resolution has altered the U.S. status as a JCPOA
“participant.” Resolution 2231 is silent on the mechanism’s
Iranian statements and the JCPOA text indicate that the
status in the event that a P5+1 government ceases
government may stop performing all or some of its JCPOA
implementing its JCPOA commitments. The United States
commitments if the Security Council extends the above-
neither describes itself nor acts as a JCPOA participant. Not
mentioned arms restrictions or invokes snapback. If Iran
only does the May 2018 memorandum mentioned above
were to end its JCPOA participation entirely, the
describe a U.S. decision to end its “participation” in the
government would be bound only by its comprehensive
agreement, but the United States is also no longer
safeguards agreement, which is of indefinite duration. Iran
performing its JCPOA commitments.
would not be bound by its Additional Protocol, should
snapback occur before Iranian ratification of that
Paragraph 10 of Resolution 2231 names the P5+1 countries
as “JCPOA participants.” But
agreement.
it is not clear that
“participants” is meant to include a P5+1 government that
In such a scenario, the IAEA would retain its monitoring
ceases performing its JCPOA commitments, or if the term
and inspection authority pursuant to Iran’s comprehensive
merely identifies the JCPOA participants in July 2015.
safeguards agreement, but the scope of this authority would
Notably, the agreement describes the P5+1 as “participants”
be narrower. For example, the agency would no longer be
when naming those states as members of the JCPOA-
able to monitor certain Iranian facilities that do not contain
established joint commission. The United States no longer
nuclear material but are associated with the government’s
participates in that commission’s activities.
enrichment program. The IAEA would also retain its
authority to verify the absence of undeclared nuclear
In an August 20 letter to Security Council President
material and activities, but the agency would have fewer
Indonesian Ambassador Dian Triansyah Djani, Secretary of
means to do so, if Iran’s additional protocol is not in force.
State Michael Pompeo initiated the snapback process by
notifying the council that Iran “is in significant non-
Moreover, Tehran would not be bound by any constraints
performance” of its JCPOA commitments. This action
on its enrichment program, which has been the main source
followed the council’s rejection of a U.S.-sponsored draft
of proliferation concern, although Iran would remain bound
resolution to extend Resolution 2231’s conventional arms-
by its NPT obligations. Significant expansion of Tehran’s
related prohibitions. The letter argued that the Resolution
enrichment program would likely decrease the amount of
2231 language cited above gives the United States the right
time necessary for Iran to produce enough weapons-grade
to invoke snapback.
highly enriched uranium for use in a nuclear weapon.
However, Djani explained in an August 21 letter to the
Prior to the JCPOA, Iran was improving its ability to
council that the “United States cannot invoke the snapback
produce fissile material, despite U.N. and other sanctions’
mechanism … because it has withdrawn from” the JCPOA.
evident success in slowing the nuclear program. At the
Consequently, he added, the August 20 letter “has no legal
time, knowledgeable IAEA and U.S. officials observed that
effect.” Similarly, a statement following a September 1
IAEA safeguards on Iran’s declared nuclear facilities would
joint commission meeting asserted that the United States
likely have detected an Iranian attempt to use them for
“could not be considered as a [JCPOA] participant State.”
producing nuclear weapons. (For more information, see
The Security Council could send the issue to the
CRS Report RL34544, Iran’s Nuclear Program: Status, by
International Court of Justice for an advisory opinion, but
Paul K. Kerr.) Nevertheless, Iran’s continuing nuclear
the council lacks an independent mechanism to adjudicate
program concerned many governments. Indeed, U.S. and
these sorts of claims, and council members typically reach
Israeli officials at the time planned for a possible attack on
political settlements to resolve such disputes. The
Iran’s nuclear program to prevent Tehran from developing a
implications of a council failure to reach such a settlement
nuclear weapon. The end of Iranian JCPOA participation
in this case are unclear.
could beget a similar situation.
Possible Iranian Responses
Iranian officials have also indicated that the government
might withdraw from the NPT in response to snapback; the
In addition to reimposing sanctions, snapback would
treaty contains a withdrawal provision. In this case, Tehran
remove other incentives for Iran to continue participating in
would not be bound either by its comprehensive safeguards
the agreement. These incentives include expiration of the
agreement or by its treaty obligations. Notably, these
restrictions on Iranian arms-related imports and exports, as
Iranian officials, echoing a longstanding government
well as missile-related imports described above.
position, have stated that Tehran would still refrain from
Snapback would also end the process by which the Security
producing nuclear weapons.
Council is to end in 2025 its consideration of the Iranian
nuclear issue. The council adopted all of the resolutions that
Paul K. Kerr, Specialist in Nonproliferation
imposed sanctions on Iran, as well as Resolution 2231,
IF11583
under Article 41 of Chapter VII, which enables the Security
Council to adopt “measures not involving the use of armed
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Iran’s Nuclear Program and U.N. Sanctions Reimposition


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https://crsreports.congress.gov | IF11583 · VERSION 5 · UPDATED

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