September 7, 2022
Reservations, Understandings, Declarations, and Other
Conditions to Treaties
Article II, Section 2, clause 2, of the U.S. Constitution (the
potentially capacious terms in a treaty and more precisely
Treaty Clause) permits the President “by and with the
lay out the United States’ understanding of their meaning.
Advice and Consent of the Senate, to make Treaties,
In one instance, the Senate added an understanding that the
provided two thirds of the Senators present concur[.]” The
term armed conflict in the International Convention for the
Senate, as part of its constitutional role in the treaty-making
Suppression of Acts of Nuclear Terrorism does not include
process, may condition its advice and consent on
internal disturbances, riots, and isolated acts of violence.
reservations, understandings, and declarations (RUDs).
These RUDs guide treaties’ content, effect, interpretation,
Declarations are statements that express the Senate’s views
and implementation.
or opinion on matters a treaty raises, often describing the
Senate’s position on policy issues. For example, in giving
Constitutional Roots of the Senate’s
advice and consent to protocols adding countries to the
Conditional Consent Authority
North Atlantic Treaty Organization, the Senate has used
Historical practice suggests that, when drafting the Treaty
declarations to express its views about the organization’s
Clause, the Framers of the Constitution intended “advice”
importance to national security. Other declarations specify a
and “consent” to be separate steps in the treaty-making
treaty’s legal domestic status—most commonly by stating
process. Under this interpretation, the President would
whether a treaty is self-executing. For background on self-
consult the Senate during treaty negotiations and seek its
execution and treaties’ role in the U.S. legal system, see
advice before asking for its final consent when negotiations
CRS Report RL32528, International Law and Agreements:
ended. Since the early years of President George
Their Effect upon U.S. Law, by Stephen P. Mulligan.
Washington’s Administration, however, Presidents have not
formally sought the Senate’s advice during treaty
Other conditions: The Senate may impose other
negotiations. Instead, the Senate has maintained an aspect
requirements under the label condition, proviso, or
of its advice function by using RUDs to influence treaties’
statement. These conditions often set forth procedural
terms and implementation.
requirements for ratifying or implementing a treaty. For
instance, the Senate has conditioned consent on
The Senate first exercised its conditional advice and
requirements that the President make certifications to the
consent authority in 1795 when it considered a commercial
Senate, produce reports, or consult certain congressional
treaty with Great Britain, known as the Jay Treaty. The
committees on issues the treaty raises.
Senate provided advice and consent “on condition” that an
article in the treaty regulating trade duties be suspended to
Among RUDs and other conditions, reservations are unique
the extent it concerned U.S. trade in the West Indies. At the
because they change a treaty’s legal effect. Other than
time, conditional consent was viewed as a peculiar feature
reservations, which are defined in international law, the
of the American constitutional system, but the practice has
label given to a condition generally derives from Senate
since become a common aspect of treaty-making
practice and usage rather than clearly delineated legal
worldwide.
frameworks or judicial decisions.
Choosing Among RUDs
Domestic Law and RUDs
The label applied to a RUD or other condition varies
The Supreme Court has recognized the Senate’s authority to
depending on its function and legal effect.
condition its consent to treaties, and lower courts have
generally given effect to RUDs. For example, when
Reservations change the United States’ legal obligations
considering the Convention against Torture and Other
under a treaty without changing the treaty’s text. For
Cruel, Inhuman or Degrading Treatment or Punishment,
example, in giving advice and consent to a treaty restricting
federal courts have held that the Senate’s understanding of
use of incendiary weapons, the Senate provided that the
the meaning of torture must apply, even if that
United States reserves the right to use those weapons in
understanding does not align with the prevailing
circumstances that would minimize civilian casualties and
interpretation in the international community.
collateral damage. A common reservation is to provide that
the United States is not bound by a treaty’s articles that
RUDs must be consistent with the Constitution, and they
require international tribunals to resolve disputes.
cannot infringe on individual rights or exercise a power the
Constitution assigns exclusively to another branch of
Understandings are interpretive statements that clarify or
government. Many commentators accept the view that,
elaborate on a treaty’s terms without altering the treaty’s
because the Senate’s conditional consent authority stems
text or legal effect. Understandings often identify broad and
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Reservations, Understandings, Declarations, and Other Conditions to Treaties
from its constitutional role in treaty-making, RUDs must
reconvening negotiations can make proposed amendments
relate to the underlying treaty.
unlikely to be adopted.
RUDs in Domestic Treaty-Making
The term amendments in the treaty context can also refer to
In the standard treaty-making process, a member of the
“floor amendments” under Senate procedural rules. During
executive branch negotiates a treaty’s terms and signs the
floor consideration of a treaty and a resolution of
completed text when negotiations end. Next, the President
ratification, proposals to amend the treaty’s text or to add
transmits the treaty to the Senate for its advice and consent.
RUDs are treated, procedurally, as “floor amendments.” For
The President may propose RUDs when transmitting
discussion of Senate rules for considering treaties and
treaties to the Senate.
RUDs, see CRS Report 98-384, Senate Consideration of
Treaties, by Valerie Heitshusen.
At the next stage, the Senate considers whether to give
advice and consent to the treaty. If it chooses to do so, it
International Law and RUDs
passes a resolution of advice and consent to ratification.
International law on RUDs is largely set forth in the Vienna
Any RUDs the Senate approved are included in this
Convention on the Law of Treaties (Vienna Convention).
resolution. The Senate’s final vote on the resolution of
The United States has not ratified the Vienna Convention,
advice and consent to ratification, including any RUDs in
but the executive branch views it as generally reflecting
that resolution, must be approved by two-thirds of Senators
customary international law, although there is disagreement
present and voting, as provided in the Treaty Clause.
on the extent to which it does so. Understandings,
declarations, and other conditions are not addressed directly
If the Senate consents to ratification, the process shifts back
in the Vienna Convention, as international law is
to the executive branch. At this point, the President decides
predominantly concerned with reservations.
whether to take the final step to ratify the treaty. As part of
that decision, the President must choose whether to agree to
The Vienna Convention permits reservations unless they
the RUDs, if any, in the Senate’s resolution. If the President
are incompatible with the treaty’s object and purpose or the
ratifies the treaty, the President is considered to have
treaty prohibits them. The Vienna Convention defines
accepted the RUDs. If the President finds the RUDs
reservation as a condition that “purports to exclude or
unacceptable, the President can decline to ratify the treaty.
modify the legal effect of certain provisions of the treaty in
their application” to the ratifying country. The label a
If ratification goes forward, the President or an executive
country attaches to a particular condition does not
branch designee signs and affixes the United States’ seal to
determine whether it is considered a reservation under
an instrument of ratification. RUDs are generally included
international law. Rather, the Vienna Convention allows
in the instrument of ratification, and some RUDs state that
countries to look beyond the label to analyze whether a
they must be included. The United States next exchanges its
condition’s substance amounts to a reservation.
instrument of ratification with the other treaty parties or
deposits it with a specified body. Most treaties define how
The Vienna Convention provides a set of rules on how
many countries must submit instruments of ratification for
countries respond to reservations. Unless the treaty provides
the treaty to enter into force.
otherwise, countries can accept reservations, object to them,
or take no action. When a country accepts a reservation, the
When the United States ratifies a treaty, the other parties to
reservation modifies the treaty’s legal effect for the party
the treaty receive notification of the United States’
that made the reservation (the reserving country) and the
instrument of ratification, including the RUDs contained in
accepting country. Acceptance may also be implied from
it. At this stage, the other parties have an opportunity to
the absence of an objection for a period of one year.
object to the United States’ RUDs through a process
defined in international law.
Countries can object to reservations, but objections
ordinarily do not prevent a treaty from entering into force.
RUDs vs. Amendments
A treaty still enters into force between the reserving country
Along with RUDs, the Senate can propose to amend a
and the objecting country unless the objector “definitely
treaty. The term amendment has different usages in this
expressed” a contrary intent. When a treaty enters into force
context. In the 19th and early 20th centuries, the Senate used
despite an objection, the treaty’s provisions related to the
the term amendment when proposing what would now be
reservation do not apply between the reserving country and
labeled as RUDs, but that usage has fallen out of favor.
the objector. For multilateral treaties, every party responds
Amendments more often refer to changes to a treaty’s text.
separately to every other country’s reservations. When one
country objects and others do not, the treaty enters into
When the Senate proposes to amend a treaty’s text, the
force, subject to the reservation, between the reserving
ratification process for the President changes. Whereas the
country and all countries that did not object.
President can ratify a treaty subject to RUDs, the President
cannot do so when the Senate includes text changes in its
Different rules apply when performing the entire treaty is
resolution of ratification. Rather, the President must reopen
essential to a treaty’s object and purpose. In those cases, all
negotiations with the other treaty parties and seek their
parties must accept a reservation for it to be given effect.
approval for the changes. Historically, when the Senate has
proposed amendments, it has been to bilateral treaties. For
Stephen P. Mulligan, Legislative Attorney
multilateral treaties, the practical and political difficulty of
IF12208
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Reservations, Understandings, Declarations, and Other Conditions to Treaties


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