A Tale of Two Principles: Snapback Mechanism through the Lens of Good Faith and Abuse of Rights-Dr. Mousa Karami

Dr. Mousa Karami- Ph. D. in International Law, Faculty of Law, University of Qom
2025/08/02

Prologue

“…It was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair…”. (Charles Dickens, A Tale of Two Cities, p. 4).

Although dispute settlement mechanisms in international law often appear to be technical and structural in nature, in practice, fundamental normative values and principles—such as ‘good faith and the ‘prohibition of abuse of rights’—play a decisive role in assessing the legitimacy of recourse to such mechanisms. The snapback mechanism, or the automatic re-imposition of sanctions, which is embedded in UN Security Council Resolution 2231 and the Joint Comprehensive Plan of Action (JCPOA), is one such instrument whose seemingly legal and legitimate form should not prevent scrutiny of the intent and purpose behind its invocation.

In 2020, the United States—despite its formal withdrawal from the JCPOA in 2018—attempted to invoke this mechanism to reinstate United Nations sanctions against Iran. This effort, fundamentally inconsistent with core normative principles, was met with firm opposition from the European Union and ultimately failed following an overwhelming majority vote in the UN Security Council. Now, there are growing indications that the European Troika (France, Germany, and the United Kingdom) may similarly seek to resort to this mechanism in October 2025. However, it must be noted that following the U.S. withdrawal, the E3 also failed to fulfill their obligations to compensate for the U.S. withdrawal by ensuring Iran’s economic benefits under the JCPOA, prompting Iran to gradually suspend some of its own commitments in response to these developments.

This blog post aims to provide a legal analysis of the potential resort by the European parties to the JCPOA to the snapback mechanism in October 2025, in light of the two fundamental principles of ‘good faith’ and the ‘prohibition of abuse of rights’ under international law. The argument unfolds in four analytical steps: it first examines the legal status of the mechanism and the precedent set by the U.S. attempt to invoke it (1); it then analyzes the two foundational principles of good faith (2) and the prohibition of abuse of rights (3) through international legal doctrine and practice; and finally (4), it demonstrates that any invocation of the snapback by the E3—if pursued without a balanced approach and genuine intent—would not only be incompatible with the JCPOA, but would also violate core normative values of international law.

1. The Legal Status of the Snapback Mechanism and the Precedent of the U.S. Invocation

The mechanism known as the ‘snapback’ or the automatic reimposition of sanctions, is one of the most legally innovative yet politically controversial instruments embedded in United Nations Security Council Resolution 2231. This mechanism was essentially designed to reassure the Western parties to the JCPOA, in the event of Iran’s non-compliance, by allowing them to restore lifted sanctions without requiring consensus. Pursuant to paragraph 11 and Annex B of Resolution 2231, any of the JCPOA participating States may allege a case of significant non-performance by Iran and refer the matter to the Security Council. If, within 30 days, the Council fails to adopt a resolution to continue the lifting of sanctions, then all previously terminated UN sanctions will automatically ‘snap back’—without the need for a vote. This very feature—the absence of a voting requirement—is the reason the mechanism has come to be known as a ‘snapback’ mechanism.

At the time of the adoption of Resolution 2231, the United States was one of the participating parties to the JCPOA and a permanent member of the UN Security Council. However, on May 8, 2018, by executive order of President Donald Trump, the United States unilaterally withdrew from the JCPOA and ceased implementing all of its commitments. Since then, the legal status of the U.S. as a ‘participant State’ in the agreement has been subject to serious dispute, as formal withdrawal from a treaty or agreement is generally understood to entail relinquishment of both the rights and obligations arising from it. In August 2020, more than two years after its official withdrawal, the Trump administration unilaterally attempted to trigger the snapback mechanism against Iran. The legal argument advanced by U.S. officials rested on the claim that Resolution 2231 refers to 'JCPOA participants' and that the U.S. was listed in its annex. Based on this, they contended that the U.S. remained a participant in structural terms and therefore retained the right to trigger the mechanism. This argument, however, was widely criticized. Thirteen out of the fifteen Security Council members—including traditional U.S. allies such as France and the United Kingdom—opposed the move, asserting that the United States, having withdrawn from the agreement, could no longer claim entitlement to invoke mechanisms embedded within it (here). Only the Dominican Republic (besides the U.S. itself) supported the action. As a result, the U.S. effort ultimately failed, and the reimposition of sanctions under Resolution 2231 did not materialize.

What is particularly noteworthy in this context is the claim of continued participation by a State that had unilaterally, publicly, and officially withdrawn from the agreement. From the perspective of international law, such conduct not only constitutes a logical and legal inconsistency, but also appears to contravene fundamental principles such as good faith in the performance of international obligations. A State cannot simultaneously absolve itself of its commitments and yet seek to benefit from the advantages provided by the agreement. This type of conduct—and the subsequent actions of the three European States, namely France, the United Kingdom, and Germany—paves the way for more in-depth analyses in the sections that follow, which examine foundational principles such as good faith and abuse of rights, before assessing the potential activation of the snapback mechanism by the European troika in light of those principles.

2. The Principle of Good Faith and Its Status in International Law

The principle of good faith is widely recognized as a foundational and structural norm of international law, playing a prominent and decisive role across various branches of this legal system. Talya Uçaryılmaz argues that this principle finds its most prominent expression in the rule of pacta sunt servanda (agreements must be kept) which constitutes the cornerstone of the law of treaties. Ziegler and Baumgartner, in their work, also describe good faith as a general principle of law and of international law that plays a significant role in the context of treaty relations. Andrew D. Mitchell even regards it as a principle of customary international law (p. 345). According to Falsafi, in his International Law on Treaties, good faith, as a general principle, permeates all norms of international law and holds particular importance across all domains of international relations (2004, pp. 443–445). Even though often unwritten, the principle of good faith has an undeniable influence on shaping the normative behavior of States and other international actors.

From a treaty-based perspective, one of the clearest expressions of this principle in contemporary international law can be found in Article 2(2) of the UN Charter, which states that “All Members shall fulfill in good faith the obligations assumed by them in accordance with the present Charter”. The duty to settle disputes in good faith is also emphasized in Article 33 of the Charter, as well as in paragraph 5 of the 1982 Manila Declaration on the Peaceful Settlement of International Disputes. Article 300 of the 1982 United Nations Convention on the Law of the Sea (UNCLOS), explicitly obliges States Parties to fulfill their obligations under the Convention in good faith and in a manner consistent with the principles of international law. Articles 18, 26, and 31 of the 1969 Vienna Convention on the Law of Treaties (VCLT) contain broad commitments related to good faith. These include the obligation not to defeat the object and purpose of a treaty prior to its entry into force, the rule of pacta sunt servanda, and the duty to interpret treaty provisions in good faith. Notably, Article 31 of the 1969 Vienna Convention, which articulates the customary rules of treaty interpretation, affirms the requirement of good faith interpretation. According to this article, treaties “shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose”. These are only some illustrative examples and not an exhaustive list. It appears that good faith, as a normative element, influences the processes of treaty interpretation, implementation, and even withdrawal. In practice, this principle obliges States to avoid distorted interpretations, formalistic implementation, or actions inconsistent with the spirit of the agreement. Thus, good faith functions both as a behavioral norm and an interpretative standard in treaty law.

The International Court of Justice (ICJ) has also invoked the principle of good faith in numerous judgments (see here). For example, in the Gabčíkovo–Nagymaros Project case (Judgment of 5 September 1997), the Court emphasized that Article 26 of the Vienna Convention requires treaties to be performed “in good faith” and further added that the principle of good faith obliges the parties to implement the treaty in a reasonable manner, in such a way that the object and purpose of the treaty may be achieved (para. 142). Similarly, in its Order on Provisional Measures in the case concerning Allegations of Genocide under the Convention on the Prevention and Punishment of the Crime of Genocide (Ukraine v. Russian Federation) (16 March 2022), the Court recalled that States parties to the Genocide Convention are required to fulfill their obligations, including Article 1, “in good faith” and in light of the object and purpose of the Convention as a whole (para. 56). Furthermore, in the North Sea Continental Shelf case (Judgment of 20 February 1969), good faith was presented as an integral part of the framework for “meaningful negotiations” and was associated with the principle of equity, aiming to prevent purely formal or symbolic behavior. The Court observed that the mere observance of procedural formalities is insufficient; without a genuine willingness to modify positions and sincere intentions, no negotiation can be considered legally effective (para. 85). In the Nuclear Tests case (Judgment of 20 December 1974), the Court unambiguously stated that good faith is a fundamental principle governing the creation and performance of legal obligations, regardless of their source (whether a treaty or a unilateral declaration). It added that international cooperation—particularly in an era of interdependence—requires mutual trust, which itself is founded on good faith (para. 46). On this basis, it can be affirmed that from the ICJ’s perspective, the principle of good faith constitutes a foundational and indispensable norm in the creation, interpretation, and implementation of international obligations. In sum, good faith is not a merely aspirational or ethical standard, but a binding legal principle that ensures the integrity and functionality of international law itself.

3. The Principle of the Prohibition of Abuse of Rights and Its Status in International Law

The principle of the prohibition of abuse of rights traces its theoretical roots to Roman private law and later to the natural law traditions of the medieval period (for a historical overview, see here)—refers to situations in which a right is formally exercised in accordance with the conditions prescribed by the rule granting that right, yet the legal outcome runs counter to the purpose of that rule. Thus, the tension at the heart of this concept lies between the rigid application of a legal rule and its true and ultimate spirit. At its core, the principle addresses the tension between the rigid application of a legal rule and the underlying spirit or purpose of that rule. It seeks to neutralize abusive’ exercises of rights by recharacterizing them as illegitimate or unlawful, relying on foundational standards of behavior such as good faith, equity, morality, justice, or respect for the ultimate object and purpose of the rule (Lenaerts, p. 1121). As Movahhed notes, the exercise of rights is not morally or legally neutral; it can be good or bad. The clearest instance of a bad-faith exercise is when the right-holder acts with malicious intent—that is, invoking a right primarily to cause harm to another (p. 17). From a theoretical standpoint, the concept of abuse of rights is commonly discussed in three distinct legal contexts: 1) Malicious intent: where the principal motive of the right-holder is to inflict harm on another; 2) Unreasonable exercise: where there is no legitimate interest or benefit in the exercise of the right, and the action results solely in harm to others; and 3) Divergence from purpose: where the right is exercised for a purpose other than that for which it was originally granted (Perillo, p. 47).

The prohibition of abuse of rights is one of the general principles of law recognized by scholars (Byers, p. 391), the International Law Commission (see here, para. 64), and States themselves (see here, para. 154) in the corpus of public international law. This principle is deeply intertwined with the concept of good faith, discussed in the previous section. Indeed, in the recent jurisprudence of the ICJ, allegations of abuse of rights by parties to a dispute have often been raised explicitly or implicitly in conjunction with the invocation of the principle of good faith (see here). These two principles may thus be seen as complementary and two sides of the same coin: good faith imposes a positive obligation, while the prohibition of abuse of rights imposes a negative duty on the right-holder not to act in a manner that undermines the legitimate expectations of others. In international law, the principle becomes particularly relevant when a State exercises its rights in a way that obstructs other States from enjoying their own rights, or when a right is invoked for a purpose other than that for which it was originally granted—particularly when it is employed coercively against another State (Kiss, p. 1). At its most basic level, the principle stands for the idea that no State may use its rights in a manner designed solely to harm others, to neutralize the effect of international norms, or to deprive another State of its legitimate entitlements. Functionally, this principle operates at the threshold between formal legality and substantive legitimacy. In treaty relations and the broader context of international law, an abuse of rights occurs when a State invokes a formally valid right, but with the underlying aim not of fair and purposive implementation, but rather of causing harm, imposing undue hardship, or generating unjustified inequality. When read alongside related concepts such as good faith, equity, and the principle of effet utile (the obligation to give treaties practical effect), the prohibition of abuse of rights emerges as a powerful doctrinal tool to prevent instrumental or manipulative uses of international legal norms.

In treaty law, Article 300 of the UNCLOS emphasizes—immediately after affirming the necessity of good faith in the performance of obligations—that the exercise of the rights, jurisdictions, and freedoms recognized in the Convention must not constitute an abuse of rights. Similarly, this prohibition is explicitly reiterated in Article 34 of the Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks, as well as in Article 33 of the Convention on the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean (5 September 2000). Parties to disputes before the Permanent Court of International Justice (PCIJ) and subsequently before the ICJ have frequently invoked this principle in a wide array of cases (on this, see: Kadkhodaei & Mohammadi, pp. 11–17), and references to it—as well as its judicial elaboration—have been increasingly prevalent in the Court’s recent jurisprudence (see here).

In sum, the principle of the prohibition of abuse of rights in international law, as a general principle of law, serves a preventive function against the formalistic and inequitable exercise of rights. By relying on standards such as good faith, equity, and teleological interpretation of legal norms, this principle helps safeguard against the circumvention of the underlying purposes of legal rules. Reflected in international instruments and the jurisprudence of the ICJ, the principle is particularly salient in the context of treaty-based rights and the procedural competencies of States, offering a mechanism to uphold legal balance among international actors. In this light, the prohibition of abuse of rights not only complements the principle of good faith, but also reinforces the normative coherence and fairness of the international legal order. The next section will evaluate the invocation of the snapback mechanism through the lens of these two foundational principles.

4. Snapback Mechanism in Light of Good Faith and the Prohibition of Abuse of Rights

In public international law, the possession of a right does not necessarily entail an unfettered discretion in its exercise. The rights of States—whether arising from treaties and international agreements or embedded within institutional mechanisms such as the United Nations Security Council—are invariably subject to fundamental principles that govern even the exercise of procedural entitlements. Among these are the obligations to act in good faith, to refrain from the abuse of rights, and to maintain proportionality between means and ends. As previously discussed, the snapback mechanism, articulated in paragraph 11 of Annex B to Security Council Resolution 2231, constitutes one such procedural right. The central question, however, is whether any State that has formally participated in the agreement can unilaterally trigger this mechanism irrespective of the agreement’s object and purpose and the aforementioned foundational principles? The answer, under international law, is unequivocally negative. As elaborated in the preceding sections, the exercise of an international right—when driven by political motives, executed in bad faith, or pursued in a discriminatory or hostile manner with the intent to inflict harm on other States—lacks legitimacy, even where that right is expressly provided for in a treaty or agreement.

From the perspective of the law of treaties, particularly under Articles 60, 62, and 65 of the VCLT, a clear distinction must be drawn between termination, suspension, and countermeasures. Article 60 recognizes the possibility of terminating or suspending a treaty in the event of a material breach, provided that the invoking State itself has complied with its obligations and follows the procedural requirements outlined in Article 65. Likewise, Article 62 permits termination or suspension only under narrowly defined circumstances involving a fundamental change of circumstances. Within this framework, the activation of the snapback mechanism—if pursued outside these procedural safeguards and merely as a means of political pressure or unilateral retaliation—cannot be deemed a lawful measure.

Even if the snapback mechanism is envisaged in the text of a resolution, its invocation by a State that has failed to uphold its commitments under the agreement, or has not engaged in the dispute settlement processes in good faith, lacks legal legitimacy and may amount to an abuse of rights. Accordingly, the assertion by certain States of a ‘procedural right’ to trigger the snapback—when exercised without genuine adherence to the JCPOA, in disregard of diplomatic dispute resolution mechanisms, or with the primary aim of exerting political or psychological pressure on Iran—cannot be considered legally tenable.

The conduct of the E3—France, Germany, and the United Kingdom—demonstrates a pattern of passivity or, at best, minimal engagement with their positive obligations under the JCPOA. For instance, in January 2020, the three European States in a Joint Statement announced the activation of the Dispute Resolution Mechanism, not with the stated aim of exerting pressure, but ostensibly to “preserve the JCPOA”. Nevertheless, from that time until 2024, not only did they fail to take effective measures to compensate for the consequences of the United States’ unilateral withdrawal from the agreement, but mechanisms such as INSTEX also remained practically inoperative. Even during the March 2021 meeting of the IAEA Board of Governors, the European parties, rather than condemning the reimposition of secondary sanctions by the United States, exerted pressure on Iran for reducing its own JCPOA commitments. This dual-track approach, from the perspective of international legal principles, may amount to a disregard of the E3’s affirmative obligations under a multilateral agreement. It also seriously undermines the legitimacy of any claim to invoke the snapback mechanism on their part, as they have acted only in response to Iran’s conduct, without having adopted a balanced or meaningful position in reaction to the United States’ fundamental breach of the JCPOA, or the absence of compensatory mechanisms by the E3 to uphold the object and purpose of the agreement.

Following the U.S. withdrawal from the JCPOA, the European parties repeatedly emphasized their “commitment to the agreement” in official statements. However, in practice, they either failed or chose not to establish effective compensatory mechanisms or offer genuine economic incentives for Iran. Instruments such as INSTEX proved practically ineffective—remaining more of a mirage than a solution—and were unable to mitigate the impact of U.S. secondary sanctions. From the perspective of international law, this situation may amount to an indirect breach of the E3’s positive obligations to ensure the implementation of the agreement. This raises a significant legal question: can a State that has not fulfilled its practical commitments to uphold a multilateral agreement resort to one of its most stringent enforcement mechanisms—namely, the snapback clause—at the moment of the agreement’s failure? Furthermore, it is necessary to ask whether Europe has actively maintained the diplomatic space for dispute resolution or whether, through passivity and disengagement from meaningful negotiations, it has in fact paved the way for legitimizing the use of the snapback mechanism. Since 2019, Europe has repeatedly issued warnings regarding Iran’s reduction of its nuclear commitments, yet it has failed to offer a balanced response to the root cause of these steps: the initial and fundamental breach by the United States. This suggests a lack of good faith and a genuine commitment to preserving the JCPOA.

If the European Troika were to unilaterally invoke the snapback mechanism in October 2025 to reimpose UN Security Council sanctions on Iran, such an action must be assessed on both legal and structural grounds. The snapback mechanism was established under a Security Council resolution and is inherently linked to the dispute resolution framework of that same body. However, if permanent or non-permanent members of the Council employ this mechanism to advance political objectives—thereby compromising its technical and impartial nature—the result would be a weakening of the Security Council’s legitimacy and authority. The JCPOA and Resolution 2231 constitute a “multi-layered legal package” grounded in diplomacy, step-by-step dispute resolution, and the possibility of returning to constructive engagement. The snapback mechanism, as the final measure in the sequence of dispute resolution steps, must not be transformed into a selective and immediate instrument of political pressure. Should States—particularly the European Troika—invoke this mechanism while disregarding diplomatic processes and without fulfilling the necessary procedural steps, the outcome will be a further erosion of trust in international legal mechanisms for dispute settlement.

Selective and instrumental use of mechanisms such as the snapback—designed exclusively to address substantiated and material breaches of international agreements—ultimately undermines the international legal order and contributes to greater instability in the interpretation of treaty law. If the European Troika, despite the United States’ effective withdrawal from the JCPOA and in the absence of any renewed negotiations or confidence-building measures, were to activate the snapback mechanism solely in response to Iran’s partial suspension or delay of its own commitments, it would send an alarming message to the international community: that international law is a flexible tool in the hands of political powers rather than a coherent framework for ensuring justice. In assessing any potential recourse by the European Troika to the snapback mechanism in 2025, it is insufficient to rely merely on a formal reference to the provisions of Resolution 2231. Rather, a comprehensive examination of these States’ conduct and obligations—from the U.S. withdrawal from the JCPOA in 2018 to the present—must be undertaken. Such an analysis is not a moral judgment, but one grounded in legal principles such as pacta sunt servanda, the duty of good faith, the prohibition of abuse of rights, and the imperative of solidarity in the implementation of multilateral treaties.

This dualistic behavior may, from a legal standpoint, signify a lack of coherence in the performance of treaty obligations. A State that only becomes active in response to Iran’s alleged breaches—while remaining silent or passive in the face of the United States’ fundamental violation—subjects its conduct to selective and politically motivated interpretation under the principles governing multilateral treaties. Ultimately, if the European Troika were to invoke the snapback mechanism in October 2025 without having taken meaningful steps toward mutual return to compliance, revived the dispute resolution pathway within the Joint Commission, or compensated Iran for the harm caused by the U.S. withdrawal and Europe’s inaction, then their legal conduct would also stand in conflict with the foundational principles of the agreement and the broader framework of public international law—particularly the principles of good faith and the prohibition of abuse of rights.

The armed attack and overt act of aggression committed by Israel against Iran on June 13, 2025 which Marko Milanović has unequivocally deemed unlawful (see here)—less than 24 hours after the adoption of a resolution by the IAEA Board of Governors against Iran,—demonstrates that bad-faith and instrumentalized use of legal mechanisms, rather than paving the path to peace, instead opens the door to war, bloodshed, and exploitation by opportunists and warmongers. It is self-evident that any potential invocation of the snapback mechanism against Iran in October 2025 would not only fail to contribute to international peace and security—thus running counter to the very raison d’être of international agreements—but would, in fact, exacerbate global instability and drive the Middle East region into deeper insecurity and turmoil.

Epilogue

In summation, the prospective invocation of the snapback mechanism by the European Troika—amidst the present context marked by Israel’s unlawful act of aggression against Iran and the E3’s prior inaction and non-compliance—cannot withstand scrutiny under the foundational principles of international law. While such a move may find textual support in the formal provisions of Resolution 2231, international legal practice, especially the jurisprudence of the ICJ, confirms that the exercise of a right in disregard of good faith and with instrumental intent amounts to an abuse of rights. The principles of pacta sunt servanda, bona fides, and non-abus de droit collectively demand that States not only adhere to the formal terms of their obligations but also uphold the object and purpose of the agreement in a coherent and reciprocal manner.

From a legal-policy perspective, transforming the snapback mechanism into an instrument of unilateral coercion subverts its function within the multilateral dispute resolution framework of the JCPOA. It delegitimizes the role of international institutions, distorts the logic of treaty law, and undermines trust in the efficacy and impartiality of international legal mechanisms. A forward-looking recommendation would thus be for the European parties to first rebuild credibility by fulfilling their positive obligations, re-engaging diplomatically through the JCPOA’s dispute resolution process, and offering verifiable economic incentives—thereby restoring the legal and ethical equilibrium necessary for invoking enforcement measures.

Ultimately, international law cannot survive as a neutral arbiter among States if its foundational principles are subordinated to political expediency. Should the snapback be invoked not as a good-faith enforcement tool but as a punitive gesture divorced from legal coherence, it will hollow out the very norms it purports to uphold. In this light, if Charles Dickens’s A Tale of Two Cities portrayed the unravelling of social order on the eve of revolution, then the present tale of two principles—good faith and the prohibition of abuse of rights—may mark the disintegration of normative trust in international law at a time when it is most urgently needed.