The Obligation Not to Prejudice the Object and Purpose of the Additional Protocol to the Safeguards Agreement in Light of Article 18 of the 1969 Vienna Convention: An Analysis of Iran’s Situation

This article examines the nature and scope of the obligation established in Article 18 of the 1969 Vienna Convention on the Law of Treaties, which requires States to refrain from acts that would defeat the object and purpose of a treaty prior to its entry into force, and assesses its implications for Iran in relation to the Additional Protocol to the Safeguards Agreement. It argues that Iran’s signature of the Additional Protocol, in the absence of an explicit declaration of intent not to become a party, has preserved its interim obligation not to defeat the Protocol’s object and purpose, although this does not entail full implementation of the Protocol before its entry into force.
The findings indicate that the obligation is rooted in the principle of good faith and has acquired a binding character in contemporary international law. The study further demonstrates that the object of the Additional Protocol is to establish enhanced transparency and verification mechanisms, while its purpose is to improve the detection of undeclared nuclear activities and strengthen international confidence in the peaceful nature of States’ nuclear programs.
The article evaluates several tests for identifying conduct that defeats a treaty’s object and purpose, including the essential elements, manifest intent, status quo, and impossible performance tests. Among these, the impossible performance test is found to provide the most effective analytical framework. Applying these criteria to Iran’s case, the study concludes that not all Iranian nuclear activities constitute a breach of Article 18. Activities conducted under safeguards supervision and within declared nuclear programs generally remain compatible with the obligation. By contrast, forms of concealment that impair the detection of undeclared nuclear activities may undermine the object and purpose of the Additional Protocol and therefore amount to a violation of Article 18.