Interpretation, Compliance, and Enforcement of Agreements


Interpretation, Compliance, and Enforcement of Agreements



In the principal work on the law of treaties, The Vienna Convention on the Law of Treaties, by Sir Ian Sinclair, the author notes that few topics in international law have given rise to such extensive controversy as the interpretation of treaties. The interpretation of disarmament and arms control treaties is further complicated because of the often highly technical content of these treaties. They may be difficult to understand even for international law scholars, who are usually not familiar with technical-military concepts and terminologies.

The purpose of the rules of treaty interpretation is to ensure that a given treaty or convention is uniformly interpreted and applied in the same way by all states parties to the Treaty. The rules of interpretation further ensure that treaties are implemented in accordance with the object and purpose of the treaty, as stated in Article 18 of the Vienna Convention on the obligation not to defeat the object and purpose of a treaty before it enters into force and thereby becomes law. Article 18 applies to states that have signed a treaty or expressed consent to be bound by the treaty, pending the formal entry into force of the treaty. In such situations, the state is obliged to refrain from acts that would be contrary to the objectives and purposes of the treaty.

Questions and disputes between states parties about treaty interpretation most often occur in connection with the application of treaties but also occur in cases of withdrawal from a treaty, or suspension of a treaty (Articles 54 and 57). The reason given by a state for its decision to withdraw or suspend is often the subject of disagreement: interpreting whether the cause is sufficient to justify the withdrawal or suspension. The decision, however, is the state’s own. Many treaties contain provisions for states parties’ right to withdrawal from a treaty “if it decides that extraordinary events, relating to the subject matter of the treaty, have jeopardized its supreme interests.” There may also be doubts about the interpretation of a treaty that builds on and replaces an earlier treaty on the same subject, for example the Biological Weapons Convention of 1972 and the 1925 Geneva Protocol, see Article 59 of the Vienna Convention on terminating or suspending the operation of a treaty and Article 30 on applying successive treaties relating to the same subject matter.

Because of the complexity of many disarmament treaties, defining the main concepts in the treaty text makes it easier to interpret the treaties in accordance with their purpose. This provides clarity for interpreting and applying the treaty. Often treaties contain standard introductory phrases such as “for the purposes of this treaty the term . . . means.” or “within the framework of this treaty the following definitions shall apply.” A different kind of contribution to treaty interpretation is given for many bilateral agreements, for example the Strategic Arms Limitation Treaty (SALT I and SALT II), and the Anti-Ballistic Missile Treaty (ABM), by having parties agree on specific interpretations. Such agreement may be expressed in statements or common understandings that the parties have agreed to in the course of the negotiating process.

Furthermore, reservations that a state party has had and which have been communicated in writing to the other treaty partners in connection with the ratification of or agreement to the treaty, may contain interpretative statements on how certain formulations or articles of the treaty shall be understood. The right to make reservations under certain circumstances is expressly stated in Article 19 of the Vienna Convention. According to this Article, a state may, when signing, ratifying, accepting, approving, or agreeing to a treaty, formulate a reservation unless the reservation is prohibited by the treaty, or the treaty provides only specified reservations, which do not include the reservation in question, to be made, or the reservation is incompatible with the object and purpose of the treaty.

A specific practice for the application of a treaty that has developed since its adoption can also create criteria or guidance for interpreting the treaty.

Vienna Convention on the Law of Treaties

The basic rules of treaty interpretation are found in the Vienna Convention on the Law of Treaties of 1969, which is based upon and codifies customary international law on treaty conclusion. The Vienna Convention, whose provisions are largely considered to reflect current customary international law, was drafted by the United Nations ILC and entered into force in 1980. As of January 2016, the Convention has 114 states parties, including China, Russia, and the United Kingdom. Forty-five countries have signed the Convention, but have not yet ratified it, including the United States, Iran, and Pakistan. France and India, among others, have not even signed the Convention.

“Ratification” means the international act whereby a state establishes, internationally its consent to be bound by a treaty (see the Convention’s article 2, paragraph 1 (b)). A ratification is carried out when the ratification document (so-called ratification instrument), approved by the respective country’s parliament and signed by its head of state, is handed over to the state or states or international organization acting as depositary(ies) for the treaty in question.

According to the Convention’s Article 31 on the general rules of interpretation, a treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in the context of the treaty and in light of the treaty’s object and purpose. In addition to the treaty text, consideration should also be given to any agreement related to the treaty that was made between all the parties in connection with the conclusion of the treaty as well as any declarations and reservations that were made by one or more of the parties in connection with the conclusion of the treaty and accepted by the other parties as an instrument related to the treaty. Together with the context, the following shall also be taken into account: any later agreement between the parties regarding the interpretation of the treaty or the application of its provisions, any later practice in the application of the treaty that establishes the parties’ agreement on its interpretation, and any relevant rules of international law applicable in the relations between the states parties. Finally, a special meaning shall be given to a term if it is established that the parties intended it that way.

According to Article 32, on supplementary means of interpretation, the preparatory work of the treaty and the circumstances of its conclusion may be taken into consideration

to confirm the meaning resulting from the application of Article 31, or

to determine the meaning when the interpretation, according to Article 31, is ambiguous or obscure, or leads to a result that is manifestly absurd or unreasonable.

The Vienna Convention applies to all kinds of disarmament and arms control treaties and conventions, whether they are concluded bilaterally between two states, multilaterally within the framework of an international organization, or regionally between countries within a specific geographic region.

The Convention is not retroactive and therefore only applies to treaties that have been concluded by states after the entry into force of the Convention with regard to such states.

Treaties concluded between states and international organizations or between international organizations are subject to the rules of the Vienna Convention on the Law of Treaties Between States and International Organizations or Between International Organizations, of 1986, which has not yet entered into force. It has forty-three participants, including twelve international organizations, among them the UN, IAEA, and OPCW (Organization for the Prohibition of Chemical Weapons). Its rules are identical to the rules of the Vienna Convention of 1969.



Pacta sunt servanda is a basic legal principle that agreements must be observed. The principle applies generally in contract law, civil law, and international law and is enshrined in Article 26 of the Vienna Convention on the Law of Treaties: “Every treaty in force is binding upon the parties to it and must be performed by them in good faith.”

When states conclude or agree to international treaties, they are expected to act in good faith and to comply with their treaty obligations. This applies to all treaties. With disarmament, arms control, and non-proliferation agreements, where vital national security interests are at stake, the parties to a treaty need to have special guarantees to ensure that the other states parties comply with the treaty and do not violate or circumvent their obligations under the treaty. Therefore, it is necessary to verify compliance with disarmament, arms control, and non-proliferation agreements to avoid international conflicts and to maintain international peace and security.

The issue of compliance – or non-compliance of states’ treaty liabilities – arises when a state party suspects, makes allegations, or presents evidence of another state party’s breach of a treaty. All recent disarmament and arms control treaties provide for procedures for violations of the treaty in the case of a state’s non-compliance – so-called compliance rules. Some cases of non-compliance by a state party to fulfill its obligations occur because of misinterpreting the treaty in question. Therefore, it is essential that the procedure for treaty violations include provisions that can guide the parties in a dispute over a treaty violation to determine whether there is well-founded suspicion or allegation of infringement, whether a demonstrated violation is serious, and whether the violation is made accidentally or deliberately. This avoids developing into a major political problem that can undermine the treaty. In the worst case scenario, non-compliance can lead to a state party’s withdrawal from the treaty, or a conflict arising between the parties. On the other hand, there must also be rules on how to act in case of serious infringements.

Control through Verification

Verification can be defined as controlling or investigating another state party’s compliance with its obligations under a disarmament or arms control agreement.1

Trust and verification are important elements in the relations between states. The purpose of verification is to detect non-compliance, deter violations, and build confidence between states parties to a treaty and ensure that the treaty is implemented and complied with effectively and correctly by all participants. Verification thus contributes to strengthening international security. Controlling whether a state complies with a treaty to which it is a party can be done through verification.

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