TEHRAN – The so-called Zangezur Corridor has emerged as an international geopolitical Question with far-reaching implications following the 2020 Nagorno-Karabakh conflict.

Some observers believe that Azerbaijani President Ilham Aliyev, frustrated in his attempts to fully incorporate the region, has sought to advance his agenda by engaging key international players, including the United States. Between 2020 and August 2025, Aliyev put forth two aggressive claims concerning Armenia’s internationally recognized territory: first, labeling Armenia’s Syunik Province as “Western Azerbaijan,” and second, demanding the “return” of approximately 500,000 ethnic Azerbaijanis who allegedly lived in the Armenian SSR before the Soviet Union dissolved.

Initially, Aliyev pursued a strategy focused on integrating Syunik into Azerbaijan. However, this approach was ultimately dropped due to strong opposition from Iran and a lack of support from Russia and the United States. The recent agreement’s inclusion of Article 5, which references the 1991 Alma-Ata Declaration and affirms respect for states’ territorial integrity and the inviolability of international borders, represents a significant shift. The Alma-Ata Declaration established the basis for recognizing the borders of post-Soviet states based on the former administrative divisions of the USSR.

From an international legal standpoint, this reference indicates a mutual acceptance by Armenia and Azerbaijan of the existing border demarcations, effectively ending further territorial claims. On the surface, this seems beneficial for Iran, as it could prevent border instability along its northwestern border and lessen the chance of a broader regional conflict. However, a more in-depth legal and strategic analysis reveals potential complications, particularly during the phases of boundary delimitation on maps and subsequent demarcation on the ground. Certain aspects of the agreement, therefore, demand close examination, given the potential risks they could pose to Iran’s access and security interests.

A central question surrounding the Zangezur issue involves the legitimacy and legal grounds for Iran's involvement, or its potential objections, as a third party in the negotiations between Armenia and Azerbaijan. The core issue is this: when two countries are negotiating matters that affect Iran's "vital interests," does international law allow Tehran to intervene, voice its concerns, or object to the outcome? Moreover, if Armenia's current government, under Prime Minister Pashinyan, were to concede any part of its sovereignty, or be pressured into a treaty that transfers territory, does Iran have the legal means to challenge or influence such agreements? And how might these legal tools be interpreted in light of the changing geopolitical landscape of the region?

International law generally recognizes that when a third state's vital interests or established rights could be impacted by a bilateral treaty or negotiation, that state has the right to express its views, raise objections, or engage in limited intervention. This right is derived from established legal principles, although the specific scope and terminology might vary depending on the specifics of each case.

Principle of Non-Binding Effect on Third States

The fundamental principle is that no international agreement can impose rights or obligations on a third state without its explicit agreement. This is enshrined in Article 34 of the 1969 Vienna Convention on the Law of Treaties. 

This principle, originating in Roman law, prevents contracts from binding or benefiting parties that were not involved, summarized by the maxim: res inter alios acta aliis nec nocet nec prodest ("a matter transacted between others does not harm or benefit a third party").

The right of objection by a third state

When two states negotiate on issues that directly affect the territorial integrity, security, or other vital interests of a third state, that third state has the right to formally object and insist that its concerns are addressed in any bilateral agreement. This right primarily stems from diplomatic practice, customary international law, and well-established legal doctrines. While not explicitly defined in treaty law, it has been consistently upheld by international courts and arbitration tribunals. 

Legally, this right flows from the principle that treaties cannot bind third states without their consent and generally enables a third party to prevent the enforcement of a treaty, or specific provisions thereof, against its will. This right is usually exercised during treaty negotiations or the formation of customary international norms. Practically, it allows a third state—like Iran—to voice its opposition through diplomatic channels, formal protests, raising the issue in international organizations, or even pursuing legal action. If the implementation of the proposed Zangezur Corridor were to threaten Iran’s northern border security, disrupt the Iran–Armenia–Georgia transit corridor, or alter the geopolitical balance in the South Caucasus, Iran could fully invoke this right to protect its interests.

Principle of the Indispensable Party

When resolving a dispute between two states necessarily involves determining the rights and interests of a third state, that third state must be included as a party to the proceedings; without its participation, the adjudication is deemed invalid. The increase in multilateral disputes and the growth of international courts and tribunals have strengthened this principle, which is reflected in the case law of the International Court of Justice (ICJ). 

Notably, the 1995 East Timor case reaffirmed the necessity of the presence of an "indispensable party." Under this rule, any dispute that substantially affects the legal interests of a third state requires that state's involvement in the settlement process. Without its inclusion, no legitimate judgment can be rendered. 

For example, if an agreement concerning the Zangezur Question were reached without Iran’s participation and it had direct security, economic, or legal ramifications detrimental to Iran, Tehran could invoke this principle to contest the validity of the agreement and demand inclusion in future negotiations.

Doctrine of the conditional right of intervention

Although intervention in the internal affairs of states is generally prohibited under international law, diplomatic measures or formal expressions of concern may be justified to safeguard vital national interests, particularly when agreements between other states threaten those interests. While not explicitly codified, this doctrine is recognized in legal scholarship and state practice, allowing states to undertake diplomatic or non-military actions when their vital interests are at risk.

For example, if the establishment of the Zangezur Corridor involves military or territorial shifts that benefit a third party, the affected state could respond with border maneuvers, issue warnings, or invoke regional mechanisms to protect its interests.

Principle of Equity

In international law, equity acts as a supplementary and interpretative principle, designed to ensure fairness in specific situations. The ICJ has notably applied this principle in cases involving maritime boundaries, disputes over shared resources, and certain tripartite conflicts. It is explicitly referenced in Article 38 of the Court’s Statute. 

For Iran, invoking the principle of equity is legally justifiable – not as a basis for military intervention, but as a legitimate foundation for demanding participation in negotiations, exercising diplomatic and legal objection rights, or even bringing complaints before international bodies. Several factors support this reliance:

(a) Length and effectiveness of shared borders: Iran shares over 40 kilometers of border with the Zangezur region, which encompasses southern Armenia and Nakhchivan. Any geopolitical change in this area directly impacts Iran’s national security, as well as its trade and transit corridors.

(b) Principle of Direct Effect: This fundamental rule determines who has the right to intervene in matters that affect their own fate. Under equity and established legal precedents, a state that would suffer tangible and direct harm from negotiations between two other states must be granted the right to comment on and participate in shaping the outcome, especially when the agreement establishes a new legal status vis-à-vis that state. This principle underpins more specific doctrines, such as the right of conditional intervention.

(c) Prohibition of unjust exclusion: Excluding Iran—despite its vital interests in the Zangezur Corridor—from all relevant negotiations would violate international equity. Removing the actor most geopolitically exposed to the issue from the decision-making process contradicts the core principles of international justice.

Principle of Good Faith

The principle of good faith is enshrined in Article 2 of the United Nations Charter and Article 26 of the Vienna Convention on the Law of Treaties. It is a fundamental requirement for treaty interpretation, negotiation conduct, the exercise of lawful rights, and even the invocation of self-defense. 

Conversely, conduct that is superficial, deceptive, manipulative, or contrary to the true purpose of legal provisions constitutes bad faith. Excluding the only state that shares a direct border with Syunik from negotiations that entail strategic changes to its northern border—especially when treaties are structured to prevent Iran from monitoring or influencing the process—amounts to a breach of the obligation to negotiate in good faith. This is particularly egregious if the treaty is used instrumentally to achieve geopolitical containment.

Bottom line 

Iran’s approach is grounded in the principle that opening transit routes, as claimed by Baku, must not come at the expense of blocking Iran’s own communication and transit corridors. Baku has employed various strategies at different levels to advance its objectives. Following the failure of its attempt to annex Syunik, Azerbaijan appears to have moderated its approach. The so-called “Trump Road” agreement makes no mention of a “corridor,” a term also absent in the November 9 Moscow agreement, though some provisions in the latter were subject to misinterpretation.

Overall, any peace plan claiming to resolve alleged transit blockages cannot logically result in the obstruction of Iran’s communication routes. Such an outcome would violate the principle of good faith. Therefore, a third-party state with vested interests retains the right to object and intervene, especially if there are grounds to suspect that an agreement is being exploited for geopolitical containment.

Salar Seyfodini is a South Caucasus expert with a Ph.D. in geopolitics from Tarbiat Modares University.