Executive Summary The joint U.S.–Israeli military operation against Iran has been described by its critics as a violation of international law. According to this view, the strikes constitute an unlawful use of force because they were not authorized by the United Nations Security Council and did not respond to an immediate Iranian attack. Such claims rely on an incorrect reading of the legal framework governing the use of force. International law prohibits aggression, but it also recognizes the inherent right of states to defend themselves against armed attack. Article 51 of the United Nations Charter explicitly affirms the right of individual and collective self-defense. Evaluating the legality of the operation against Iran therefore requires examining the broader strategic context in which it occurred. For more than four decades, the Islamic Republic of Iran has pursued a sustained campaign of hostility against Israel through a regional network of proxy organizations, including Hezbollah, Hamas, and other armed groups that have repeatedly attacked Israeli territory with Iranian support. Iran has simultaneously expanded its ballistic missile capabilities and advanced its nuclear program while openly declaring its intention to eliminate the State of Israel. In an era of proxy warfare and indirect aggression, international law cannot be interpreted in ways that allow states to wage sustained attacks through intermediaries while claiming immunity from response. The debate surrounding the operation against Iran also highlights a broader challenge for democracies, particularly in Europe. International law was largely developed by free nations to restrain aggression, yet authoritarian regimes invoke its language while violating its principles. Preserving the credibility of the international legal order requires solidarity among democracies and moral clarity about the right to self-defense. Introduction The joint U.S.–Israeli military operation against Iran has been described by many European commentators as a violation of international law. In Europe, the accusation of illegality has become almost reflexive whenever force is used outside the explicit authorization of the United Nations Security Council. According to this view, the strikes against Iran constitute an unlawful act of aggression and risk undermining the very legal order that democratic states claim to defend. Such claims do not withstand scrutiny. International law should not be a rhetorical instrument invoked in moments of political disagreement. It is a body of norms designed to regulate the use of force while preserving the fundamental right of states to defend themselves against aggression. The United Nations Charter, which remains a cornerstone of the contemporary international legal order, explicitly recognizes this principle. Article 51 affirms the “inherent right of individual or collective self-defence” in the event of an armed attack. The legal question surrounding the operation against Iran therefore cannot be answered by invoking a general prohibition on the use of force alone. It requires a serious examination of the strategic context in which that force has been used. That context is often overlooked in current debates. Since the establishment of the Islamic Republic in 1979, Iran has pursued a sustained strategy aimed at eliminating the State of Israel, combining ideological commitment to Israel’s destruction with the development of military capabilities intended to realize that objective. Over the past four decades, Tehran has built and armed a network of proxy organizations across the Middle East, most notably Hezbollah in Lebanon, but also Hamas, Palestinian Islamic Jihad, and various militia groups operating from Syria, Iraq, and Yemen. These organizations have carried out repeated attacks against Israel while benefiting from Iranian financing, training, weapons, and strategic direction. More recently, Iran itself has demonstrated its willingness to launch direct missile and drone attacks against Israeli territory while continuing to advance its ballistic missile and nuclear programs. This pattern of conduct raises a central legal question: how should international law address situations in which a state conducts a sustained campaign of aggression through proxies while simultaneously developing the strategic capabilities to threaten another state’s very survival? The answer cannot simply be that the targeted state must remain passive until the most destructive phase of that campaign is realized. International law was never intended to impose such a requirement. The legality of the operation against Iran must therefore be assessed within the broader framework of the law governing self-defense and armed conflict. When examined in that context, the claim that the operation is illegal appears far less convincing than many of its critics suggest. Indeed, a careful reading of international law, combined with an understanding of the strategic realities of modern warfare, suggests that the case for legality is far stronger than is often acknowledged. Beyond the immediate legal question, however, the controversy surrounding the operation reveals a deeper challenge confronting democracies. International law was largely shaped and promoted by the liberal democracies that emerged victorious from the Second World War and later prevailed in the Cold War. Yet authoritarian regimes have learned to use the language of international law while simultaneously undermining the norms that sustain it. When such regimes wage war through proxies, threaten their neighbors’ existence, and exploit legal rhetoric to delegitimize defensive action, democracies must uphold the rule of law without allowing it to be manipulated into a shield for aggression. This paper examines the legal and strategic dimensions of the U.S.–Israeli operation against Iran in that broader context. It argues that the operation can be understood as a legitimate exercise of the right of self-defense under international law, particularly in light of Iran’s long-standing campaign of proxy warfare and its declared intention to eliminate the State of Israel. More broadly, the paper contends that democracies must approach the interpretation of international law with moral clarity. The defense of the international legal order ultimately depends not only on the precision of legal arguments but also on the willingness of free nations to resist those who seek to exploit the language of law while rejecting its underlying principles. 1. Iran’s Long War Against Israel Any legal assessment of the U.S.–Israeli operation against Iran must begin with the context in which it occurred. The debate surrounding the legality of the operation often proceeds as if it represented a sudden and isolated escalation. In reality, the confrontation between Iran and Israel has developed over decades and has long involved repeated uses of force, both direct and indirect. Ignoring that history risks producing a distorted legal analysis detached from the realities that international law is meant to regulate. From its inception in 1979, the Islamic Republic of Iran defined opposition to Israel as a central component of its ideological identity and foreign policy. The revolutionary leadership in Tehran repeatedly declared that the elimination of the “Zionist regime” was a central objective. These declarations were not merely rhetorical. Over the following decades, Iran invested substantial financial and military resources in building a regional network of armed organizations whose purpose was to confront Israel through sustained asymmetric warfare. The most significant of these organizations is Hezbollah, established in Lebanon in the early 1980s with direct Iranian support. Iran’s Islamic Revolutionary Guard Corps (IRGC), and particularly its Quds Force, played a central role in training, financing, and equipping Hezbollah, transforming it into one of the most heavily armed non-state actors in the world. Over time Hezbollah developed a vast arsenal of rockets and missiles capable of striking deep into Israeli territory, as well as advanced operational capabilities that allowed it to wage sustained military campaigns against Israel. Iran’s support for anti-Israeli militant groups has not been limited to Lebanon. Tehran has also provided financial assistance, weapons, and training to Hamas and Palestinian Islamic Jihad in the Gaza Strip. These organizations have carried out repeated rocket attacks against Israeli cities and have engaged in large-scale armed confrontations with Israel. Iranian assistance has contributed significantly to the development of their military capabilities, including missile production and advanced weapons systems. In recent years, Iran has expanded this strategy by supporting additional militia networks across the region. Iranian-backed armed groups operating from Syria and Iraq have repeatedly threatened Israeli targets, while the Houthi movement in Yemen has demonstrated the capacity to launch long-range missiles and drones toward Israeli territory. Through this network of proxy forces, Iran has effectively surrounded Israel with armed organizations capable of conducting attacks from multiple fronts. This strategy of proxy warfare has been complemented by the development of increasingly sophisticated military capabilities within Iran itself. Over the past two decades, Tehran has invested heavily in ballistic missile technology and unmanned aerial systems, creating one of the largest missile arsenals in the Middle East. These capabilities provide Iran with the ability to strike targets across the region, including within Israel. The growing role of direct Iranian action became particularly evident in April 2024, when Iran launched hundreds of missiles and drones toward Israel in an unprecedented direct attack. Although most of these projectiles were intercepted through a coordinated defensive effort involving Israel and several of its partners, the episode marked a significant escalation in the long-running confrontation between the two states. It demonstrated that Iran was prepared not only to arm and direct proxy forces but also to employ its own military capabilities directly against Israel. At the same time, Iran has continued to advance its nuclear program while expanding the range and precision of its ballistic missile systems. Iranian leaders have repeatedly combined these technological developments with public statements questioning Israel’s legitimacy and predicting its eventual disappearance. Taken together, these elements—proxy warfare, missile development, and nuclear advancement—constitute aggression. While the methods employed have often relied on indirect forms of warfare, the underlying objective has remained consistent: to weaken Israel militarily and strategically while maintaining the capability to inflict increasingly severe damage over time. This long-term pattern of aggression is essential for understanding the legal debate surrounding the recent U.S.–Israeli operation against Iran. International law does not operate in a vacuum. The legal rules governing the use of force must be interpreted in light of the factual circumstances in which states act. When those circumstances involve decades of proxy warfare, repeated attacks by armed groups supported by a state, and the development of military capabilities designed to threaten another state’s survival, the legal analysis necessarily becomes more complex than the simplified narratives often presented in public debate. 2. Self-Defense and the Law of Armed Conflict The legal debate surrounding the U.S.–Israeli operation against Iran centers on one fundamental question: under what circumstances does international law permit the use of force in self-defense? Critics of the operation argue that it violates the United Nations Charter’s prohibition on the use of force because it was not authorized by the Security Council and did not respond to a single, clearly identifiable Iranian attack immediately preceding the strikes. Yet this interpretation rests on a simplified reading of the legal framework governing the use of force and overlooks both the evolution of international law and the strategic realities of modern conflict. The cornerstone of the contemporary legal order governing the use of force is the United Nations Charter. Article 2(4) establishes a general prohibition on the use of force in international relations, reflecting the international community’s determination after the Second World War to prevent wars of aggression. At the same time, the Charter explicitly recognizes that states retain an inherent right to defend themselves. Article 51 affirms the “inherent right of individual or collective self-defence if an armed attack occurs.” This provision acknowledges a fundamental principle that long predates the Charter itself: the right of states to protect their security and survival when confronted with armed aggression. The interpretation of Article 51 has been the subject of extensive legal debate. At its core, however, the doctrine of self-defense has traditionally rested on two widely accepted criteria: necessity and proportionality. These principles, articulated in the nineteenth century in the well-known Caroline correspondence between the United States and the United Kingdom, remain central to contemporary international law. According to this formulation, the use of force in self-defense must respond to a threat that is necessary to address and must be proportionate to the objective of removing that threat. While these principles are broadly accepted, their application has evolved as the nature of warfare has changed. One of the most significant areas of debate concerns the question of imminence. A narrow interpretation of Article 51 suggests that a state may use force in self-defense only after an armed attack has already occurred. Yet many states and legal scholars have long recognized that such an interpretation may be unrealistic in circumstances where waiting for an attack to materialize could expose a state to catastrophic harm. The concept of anticipatory self-defense emerged precisely from this concern. Under this doctrine, a state may act in self-defense when an attack is imminent and when delaying action would make effective defense impossible. The Caroline formulation itself referred to situations in which the necessity of self-defense is “instant, overwhelming, leaving no choice of means and no moment for deliberation.” Although debates continue over how strictly the requirement of imminence should be interpreted, state practice over the past decades has increasingly reflected a more flexible understanding of this principle, particularly in the context of modern weapons systems capable of inflicting large-scale destruction within very short timeframes. The strategic environment of the twenty-first century further complicates this legal framework. Contemporary conflicts frequently involve indirect forms of warfare in which states rely on proxy forces, militias, and non-state actors to conduct attacks while attempting to preserve a degree of plausible deniability. International law has gradually adapted to this reality by recognizing that the responsibility of a state for armed attacks does not disappear simply because those attacks are carried out through intermediaries. When a state organizes, finances, equips, and directs armed groups that repeatedly carry out attacks against another state, the distinction between direct and indirect aggression becomes increasingly difficult to sustain. This principle has important implications for the confrontation between Iran and Israel. As discussed in the previous section, Iran has for decades developed and supported a network of armed organizations that have repeatedly engaged in hostilities against Israel. These groups have benefited from Iranian training, weapons, financing, and strategic coordination. The relationship between Iran and several of these organizations, most notably Hezbollah, has long been widely documented by governments and independent observers alike. In such circumstances, treating the actions of these groups as legally detached from the state that enables and directs them risks creating a significant loophole in the international legal framework governing the use of force. Another important legal perspective concerns the characterization of the conflict itself. International humanitarian law traditionally defines an international armed conflict as a situation in which hostilities occur between states or between a state and forces acting on behalf of another state. Under this framework, the persistence of hostilities over time can sustain the existence of an armed conflict even in periods when direct large-scale combat temporarily subsides. From this perspective, the confrontation between Iran and Israel may be understood as a prolonged conflict characterized by indirect warfare, intermittent escalation, and the use of proxy forces. Based on this interpretation, the recent military operation against Iran does not represent the sudden initiation of hostilities but rather a new phase within an already existing conflict. This does not eliminate the relevance of the rules governing self-defense, but it places the legal analysis within a broader framework in which the use of force occurs in the context of ongoing hostilities rather than as a wholly new resort to armed force. Taken together, these considerations suggest that the legal debate surrounding the operation against Iran cannot be reduced to a simple binary choice between legality and illegality. The principles governing self-defense were developed in a different strategic environment, and their application must take into account the transformation of warfare in the contemporary international system. Proxy warfare, missile technologies, and long-term campaigns of indirect aggression all challenge rigid interpretations of the legal framework governing the use of force. A careful reading of international law therefore indicates that the case for self-defense in this context is both serious and legally grounded. The right of states to defend themselves against sustained armed aggression remains a central principle of the international legal order. Interpreting that principle in a way that ignores the realities of modern conflict would risk undermining the very purpose for which the law was originally designed: the protection of states and societies from acts of violence that threaten their security and survival. 3. Proxy Warfare and the Transformation of Self-Defense One of the most significant challenges facing the contemporary law governing the use of force is proxy warfare. Countries can pursue their objectives not through direct military confrontation but through networks of armed groups that operate with their support, coordination, and guidance. This strategy allows aggressive states to exert military pressure on adversaries while attempting to avoid the political and legal consequences associated with open interstate warfare. The resulting ambiguity complicates the application of international law and raises fundamental questions about how the right of self-defense should be interpreted in an era of indirect conflict. Iran has been one of the most systematic practitioners of this strategy. Over the past four decades, Tehran has developed an extensive regional network of armed organizations that operate across the Middle East. These groups include Hezbollah in Lebanon, Hamas and Palestinian Islamic Jihad in Gaza, various militia organizations in Syria and Iraq, and the Houthi movement in Yemen. While each of these actors maintains its own local agenda, their military capabilities have been significantly shaped by Iranian support. Iran’s Islamic Revolutionary Guard Corps (IRGC), particularly its Quds Force, has played a central role in providing training, weapons, financing, intelligence, and operational guidance to many of these organizations. The purpose of this network has been strategic as well as ideological. By empowering armed groups positioned along Israel’s borders and throughout the region, Iran has created what many analysts describe as a “forward defense” posture. Rather than confronting Israel directly through conventional interstate warfare, Tehran has sought to exert pressure through multiple fronts while preserving a degree of plausible deniability regarding the origin of attacks. This approach has allowed Iran to challenge Israel’s security while complicating the legal and diplomatic response available to its adversaries. From the perspective of international law, however, the reliance on proxy forces raises a critical issue: whether a state can avoid responsibility for armed attacks by delegating their execution to non-state actors. If the answer were affirmative, the legal framework governing the use of force would contain a major loophole. States could engage in sustained military aggression while formally denying involvement, thereby constraining the ability of targeted states to invoke the right of self-defense against the true source of the threat. For this reason, international law has long recognized that states may bear responsibility for the actions of armed groups operating on their behalf. Jurisprudence and state practice have developed criteria for determining when the conduct of such groups can be attributed to a state. In its landmark 1986 judgment in Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States), the International Court of Justice held that a state may be responsible for the actions of armed groups when it provides substantial support and exercises effective control over their military operations. Subsequent jurisprudence, including the 1999 Appeals Chamber judgment in Prosecutor v. Tadić, further clarified that such responsibility may arise when a state organizes, equips, finances, or coordinates the activities of armed groups engaged in hostilities. While the precise legal thresholds remain debated, the underlying principle is widely accepted: when a state organizes, equips, finances, and directs armed groups that carry out attacks, it cannot claim complete legal separation from those actions. In practice, the relationship between Iran and several of the organizations within its regional network meets many of these criteria. Hezbollah has long functioned not merely as an allied militia but as a strategic partner closely integrated into Iran’s regional military architecture. Iranian military assistance has been essential to Hezbollah’s development into a force possessing tens of thousands of rockets and missiles capable of reaching Israeli population centers. Similar patterns of support can be observed in Iran’s relationship with Palestinian armed groups in Gaza and with various militia organizations operating in Syria and Iraq. The growing role of proxy warfare, therefore, challenges restrictive interpretations of the law governing self-defense. If international law were interpreted in a manner that treats attacks carried out by such groups as legally detached from the states that enable them, the result would be a form of strategic asymmetry. States employing proxy forces could conduct sustained campaigns of violence while shielding themselves from direct response, whereas states subjected to those attacks would face severe legal and political constraints when attempting to neutralize the source of the threat. Such an outcome would run counter to the underlying logic of the international legal order. The prohibition on the use of force was designed to prevent aggression, not to provide aggressors with new methods of circumventing accountability. Allowing states to wage war indirectly while invoking legal protections against retaliation would undermine the balance that the United Nations Charter sought to establish between the restriction of force and the preservation of the right of self-defense. The controversy surrounding the U.S.–Israeli operation against Iran is a case in point. Iran’s reliance on a regional network of armed organizations has been a defining feature of its strategy for decades. Evaluating the legality of defensive action without taking that strategy into account would risk ignoring one of the most significant developments in contemporary warfare. Understanding how proxy conflict reshapes the interpretation of self-defense is therefore essential to assessing the legal and strategic implications of the current confrontation. 4. The Political Instrumentalization of International Law The legal debate surrounding the U.S.–Israeli operation against Iran cannot be understood solely as a technical dispute about the interpretation of the United Nations Charter. It also reflects a broader political and strategic dilemma confronting democratic states in the contemporary international system. At the United Nations, the language of international law is being invoked not only as a framework for regulating the use of force but also—indeed, mostly—as a political instrument deployed in geopolitical competition. This development raises an important question: how can democracies uphold the rule of law without allowing legal norms to be manipulated in ways that ultimately weaken the very order they were designed to protect? International law as it exists today was largely shaped by the liberal democracies that emerged victorious from the Second World War and later prevailed in the Cold War. The United Nations Charter and the broader body of international legal norms governing the use of force were conceived as mechanisms to constrain aggression and stabilize international relations. These institutions reflected a balance between two fundamental objectives: preventing wars of conquest while preserving the right of states to defend themselves against threats to their security and survival. However, authoritarian regimes that openly challenge the international order have learned to adopt the language of international law while disregarding its underlying principles. Russia has invoked legal arguments about sovereignty and self-determination while conducting military interventions in neighboring states. China frequently appeals to international legal concepts while pursuing expansive territorial claims in the South China Sea that have been rejected by international tribunals. Iran, for its part, regularly denounces the use of force by its adversaries while simultaneously sponsoring armed groups that carry out attacks across the Middle East. This pattern reflects a broader strategy in which legal rhetoric becomes a tool of politics. By framing the actions of democratic states as violations of international law, authoritarian regimes seek to delegitimize defensive measures while diverting attention from their own conduct. The effectiveness of this approach depends in part on the willingness of democratic societies to hold themselves to high legal and moral standards. While such standards are an essential component of democratic legitimacy, they can also create vulnerabilities when adversaries exploit legal language selectively and strategically. The debate surrounding the operation against Iran illustrates this tension. Much of the criticism directed at the operation has focused narrowly on whether the use of force was formally authorized by the United Nations Security Council or whether it responded to an immediate and unmistakable armed attack. Such arguments overlook the broader pattern of aggression that has characterized Iran’s regional strategy for decades. For democracies, the challenge is therefore not simply to defend the legality of particular military operations but to preserve the integrity of the international legal order itself. That order cannot survive if its rules are interpreted in ways that reward states that systematically exploit legal ambiguity while penalizing those that attempt to defend themselves against sustained aggression. The credibility of international law ultimately depends on its ability to address the realities of modern conflict rather than remaining confined to conceptual frameworks developed for an earlier era of interstate warfare. For Europe, in particular, the controversy surrounding the operation against Iran raises important questions about the relationship between legal principles and strategic responsibility. European states have long been among the most vocal defenders of the international legal order, emphasizing the importance of multilateral institutions and legal norms in regulating international affairs. Yet this tradition of legalism risks evolving into a form of detachment when legal arguments are applied without attention to the security realities faced by democratic allies. The confrontation between Iran and Israel illustrates the limitations of such an approach. A regime that openly calls for the destruction of another state while building the military capabilities to pursue that objective presents a challenge that cannot be addressed through legal formalism alone. The purpose of international law is not to create procedural obstacles that prevent states from defending themselves against existential threats. Rather, it is to provide a framework within which security and stability can be maintained. In this sense, the debate over the legality of the operation against Iran reflects a broader test for democratic states. Upholding the rule of law requires more than the mechanical application of legal formulas. It requires the willingness to interpret legal principles in a manner consistent with the fundamental purpose of the international order: the protection of states and societies from aggression. Democracies that helped create the modern legal order bear a particular responsibility to ensure that it remains both principled and effective. Doing so requires moral clarity about the nature of contemporary threats and the recognition that defending the rule of law entails supporting threatened democracies that wouldn’t stand a chance to fight and survive with a restrictive reading of the right of self-defense. Conclusion The debate surrounding the legality of the U.S.–Israeli operation against Iran illustrates the growing tension between the traditional legal framework governing the use of force and the evolving realities of modern conflict. Critics who describe the operation as a clear violation of international law rely on a narrow interpretation of the United Nations Charter that treats the prohibition on the use of force in isolation from the equally fundamental right of states to defend themselves against aggression. When examined within its broader strategic context, however, the legal picture appears far more complex. For more than four decades, the Islamic Republic of Iran has pursued a sustained campaign of hostility against the State of Israel, combining ideological commitment to Israel’s destruction with the systematic development of proxy warfare capabilities across the Middle East. Armed organizations supported by Iran have repeatedly launched attacks against Israeli territory, while Tehran has continued to expand its ballistic missile arsenal and advance its nuclear program. In such circumstances, the legal analysis cannot reasonably be confined to the question of whether a single Iranian missile strike immediately preceded the most recent military operation. International law does not require states to remain passive in the face of sustained and escalating threats to their security. Article 51 of the United Nations Charter explicitly recognizes the inherent right of self-defense, and the evolution of state practice has increasingly acknowledged the challenges posed by proxy warfare, missile technology, and other forms of indirect aggression. Interpreting the law in a manner that ignores these realities would risk creating a dangerous asymmetry in which states that wage war indirectly are effectively shielded from accountability while those defending themselves face accusations of illegality. The controversy surrounding the operation against Iran also reflects a broader dilemma for democracies. International law was largely constructed by the free nations that emerged victorious from the major conflicts of the twentieth century. Yet today, authoritarian regimes invoke the language of international law while simultaneously undermining it. When legal arguments are employed selectively to delegitimize defensive action and shield those who engage in sustained aggression, democracies must respond with solidarity and moral clarity. The defense of the international legal order ultimately requires not only fidelity to its rules but also the political will to ensure that those rules are not turned into instruments that shield aggression rather than restrain it.