Legal Obligations of Signatories and Parties to Treaties

In judging different moot court competitions during the past two months, I have noticed several competitors did not understand the difference between signatories and parties to a treaty. This posting provides an overview of when a treaty is legally binding upon a State and a few examples. It contains, and expands upon, information in the earlier Background Fact Sheet on What Is International Law?.

If you have questions, suggestions, or clarifications, please email me (see left nav). If you are currently competing in the Jessup, I will not be able to answer your questions until after the conclusion of the International Rounds, March 22-27. Hope you find the following to be helpful.

What Is the Difference Between a Signatory and a Party to a Treaty?

When you look at the “status” of a treaty, you will find two listings: signatories and parties. The status will indicate the date upon which each State became a signatory and/or a party.

  A Signatory State to a Treaty A Party to a Treaty
Description The term “signatory” refers to a State that is in political support of the treaty and willing to continue its engagement with the treaty process. This intent is codified as a “signature” submitted to the qualifying international body with oversight of the treaty or the authoritative body defined by the treaty.

Essentially, the treaty has not yet entered into force for that particular State.

States may sign a treaty in advance of their domestic processes required for treaty ratification. For example, in the United States, the President has the legal authority to “sign” the treaty; the President cannot ratify the treaty without the consent of the U.S. Senate.

The term “party” refers to a State that gives its explicit consent to be bound by the treaty. This explicit consent generally is in the form of an instrument of ratification, acceptance, approval, or accession. The State submits this instrument to the appropriate authoritative body for that treaty. If all the formal requirements are met and the instrument is accepted, the State officially becomes a party to the treaty.
Legal Obligations A signatory State agrees to act, in good faith, “not to defeat the object and purpose” of the treaty. See VCLT Article 18.

A signatory is not legally bound by a treaty’s specific provisions and obligations. For example, if the treaty imposed a requirement of a 70% reduction of mercury emissions over five years, a signatory state would not be legally bound to meet that 70% target. A signatory state with a lesser reduction of its mercury emissions could still be legally compliant under international law. Consider, however, whether a signatory state that doubles its mercury emissions over those five years would be acting in contradiction to the purpose of the treaty to decrease global mercury emissions.

A party is legally bound by the provisions within the treaty and accepts all the treaty’s obligations, subject to legitimate reservations, understandings, and declarations (RUDs).
Termination A State may choose to withdraw its signature. For example, on May 6, 2002, the United States withdrew its signature from the Rome Statute. Some treaties define how, and when, States may terminate a treaty. For example, the Nuclear Nonproliferation Treaty (NPT) requires a State to provide three months advance notice. Notably, North Korea asserts that it has met that requirement by aggregating the days of separate notifications. The United States withdrew in 2002 from the bilateral Anti-Ballistic Missile Treaty upon completion of its 6-month advance notice to Russia.

Many treaties are silent on withdrawal procedures.

Under VCLT Article 62, a party may be able to modify or terminate a treaty due to an unforeseeable and fundamental change of circumstances. The doctrine of necessity may be used as a defense to justify a modification or termination of a treaty. This principle does not apply to treaties defining geographical boundaries. For more information, including the five-point criteria used by the International Court of Justice, see the ICJ case of Gabcikovo-Nagymaros Project, Hungary v. Slovakia (applying Article 62).

Treaty Not In Force Under VCLT Article 18, a signatory cannot act “to defeat the object and purpose of the treaty” when the treaty is pending entry into force. If a treaty has not yet entered into force, its legal obligations are not enforceable. You might see the term “Contracting State” or “Contracting Government” used to refer to a State that has ratified a treaty that is not yet in force.

Under VCLT Article 18(b), Contracting States cannot act “to defeat the object and purpose of the treaty” pending the entry into force of the treaty, “provided that such entry into force is not unduly delayed.”

Vienna Convention on the Law of Treaties, Article 18

Obligation not to defeat the object and purpose of a treaty prior to its entry into force

A State is obliged to refrain from acts which would defeat the object and purpose of a treaty

(a) it has signed the treaty or has exchanged instruments constituting the treaty subject to ratification,
acceptance or approval, until it shall have made its intention clear not to become a party to the treaty; or
(b) it has expressed its consent to be bound by the treaty, pending the entry into force of the treaty
and provided that such entry into force is not unduly delayed.


Vienna Convention on the Law of Treaties, Article 62

Fundamental change of circumstances

1. A fundamental change of circumstances which has occurred with regard to those existing at the
time of the conclusion of a treaty, and which was not foreseen by the parties, may not be invoked as a
ground for terminating or withdrawing from the treaty unless:

(a) the existence of those circumstances constituted an essential basis of the consent of the parties to
be bound by the treaty; and

(b) the effect of the change is radically to transform the extent of obligations still to be performed
under the treaty.

2. A fundamental change of circumstances may not be invoked as a ground for terminating or
withdrawing from a treaty:

(a) if the treaty establishes a boundary; or

(b) if the fundamental change is the result of a breach by the party invoking it either of an obligation
under the treaty or of any other international obligation owed to any other party to the treaty.

3. If, under the foregoing paragraphs, a party may invoke a fundamental change of circumstances
as a ground for terminating or withdrawing from a treaty it may also invoke the change as a ground for
suspending the operation of the treaty.



Additional Resources on Inside Justice

Research on Treaties

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