International law is unequivocal: the war against Iran is illegal

The myth of “preventive” action

The United States and Israel have presented their military action against Iran as a series of “preventive strikes”, supposedly intended to neutralize imminent threats from the Iranian regime and prevent Iran from acquiring nuclear weapons.

Such an argument, widely echoed by much of the Western media, may appear plausible at first glance. However, a rigorous examination shows that these operations cannot reasonably be classified as preventive, nor can they be justified as acts of self-defense under international law. The legal situation is unequivocal: the war initiated by the Trump administration against Iran is illegal.

But before examining the legality of the use of force, it is worth recalling an element frequently omitted from the public debate. In the early 2000s, Iran’s Supreme Leader, Ayatollah Ali Khamenei, issued a fatwa declaring that the development, possession and use of nuclear weapons were contrary to Islam. Iranian authorities have reiterated for years that this religious prohibition constituted a binding constraint on the Iranian state. Until the events that official media describe as his death, Khamenei was presented by the Iranian government itself as the main guarantor that Iran would not develop a nuclear weapon for doctrinal and moral reasons, not merely strategic ones. This context is relevant when assessing current allegations regarding the imminence of an Iranian nuclear threat.

The legal framework of international law

The Charter of the United Nations strictly prohibits the unilateral use of force by states, except in two very specific circumstances:

when the use of force has been authorized by the UN Security Council; or
when it is exercised in self-defense.

Neither the United States nor Israel requested or obtained authorization from the Security Council before launching the attacks on Saturday. Consequently, self-defense is the only possible justification under international law. When examined in light of the facts, however, that justification does not hold.

Invoking Israel’s right to self-defense

Israel argues that it cannot be required to wait until Iran is capable of launching a nuclear attack before acting in self-defense. International law does allow anticipatory self-defense in very limited circumstances, specifically when an armed attack is already underway. For example, if Iran were to launch a ballistic missile, Israel would have the right to intercept it before it reached its target. Such an interceptive action would constitute lawful anticipatory self-defense.

However, international law clearly distinguishes between this form of legitimate anticipation and the preventive or precautionary use of force, which is not permitted.

Preventive self-defense and its limits

Preventive self-defense occurs when a state claims that an imminent threat exists, even though the attack has not yet begun, and decides to strike first in order to pre-empt it. In this case, Israel argues that Iran represented an imminent threat that justified a first strike.

This reasoning is problematic. Many states distrust the intentions of other states. If the subjective perception of imminence were sufficient, numerous countries in the Middle East could claim the same right to launch preventive strikes against Israel. Moreover, there is no reliable mechanism to independently verify whether such an alleged imminent threat was real.

According to Reuters, the attack had been planned for months and the specific date had been set weeks in advance. This significantly undermines the claim that an Iranian attack was so imminent that it required an immediate response. There is an academic debate regarding the precise boundary between lawful interception and unlawful preemption. States of the Global Majority generally adopt a strict interpretation: unless an attack is actually underway, the use of force is illegal. Many states in the Global North maintain a more flexible interpretation, according to which the use of force may be lawful if the attack is “imminent”, even if it has not yet begun.

The problem lies in defining what “imminent” means. In theory, it could include situations in which preparations for an attack are clearly identifiable even if weapons have not yet been launched, such as the discovery of German military preparations shortly before the beginning of the Blitzkrieg. In practice, however, this margin of discretion lends itself to abuse. A well-known example is the American claim that Iraq was planning an “imminent” attack using alleged weapons of mass destruction.

For this reason, states of the Global Majority categorically reject the use of preventive force. The evidence supporting claims of imminence can easily be falsified or withheld under the pretext of “national security”. When a state considers preventive action necessary, it should present its evidence to the UN Security Council and request authorization.

Without such oversight, preventive self-defense risks becoming little more than a legal pretext for political realism. The most powerful states could attack weaker ones at will, while the latter would have no equivalent right. In such a scenario, power would replace law.

Preventive self-defense against future threats

Preventive self-defense in the broader sense must be distinguished from preemption. It refers to the use of force against a potential future threat that might materialize at some indeterminate point.

This is essentially the argument currently used by the United States and Israel regarding Iran, regardless of the terminology used in public discourse. The thesis is that Iran could develop nuclear weapons in the future and eventually use them against Israel, making preventive action preferable.

However, there is no evidence that Iran was close to developing a nuclear weapon. In fact, just eight months ago Donald Trump publicly declared that Iran’s main nuclear enrichment facilities had been “completely and totally obliterated” following U.S. participation in Israel’s twelve-day war against the country. He repeated this claim as recently as last week during his State of the Union address, stating that the United States had “obliterated Iran’s nuclear weapons program with an attack on Iranian soil”.

In any case, preventive self-defense is illegal under international law. States do not have a blank check to decide which other states might constitute a future threat. China cannot invade Taiwan preventively, nor can Russia invade Finland preventively.

Humanitarian intervention in the name of the Iranian people

The United States has also argued that it acted in self-defense on behalf of the Iranian people, invoking a humanitarian justification for the use of force.

The use of force for purely humanitarian reasons, without authorization from the UN, is not an accepted justification under international law. Some states have defended this reasoning in the past, such as Belgium during NATO’s bombing campaign against Serbia in 1999, or the United Kingdom following the use of chemical weapons by Syria in 2018. Nevertheless, these positions remain deeply controversial.

States of the Global Majority have consistently rejected so-called “humanitarian interventions”, arguing that states of the Global North are not reliable actors when they claim to act for genuinely humanitarian reasons. They point to the absence of intervention in situations where Western interests were not involved, such as Rwanda in 1994, or in cases where those interests coincided with mass atrocities, such as in Gaza since 2023.

The very concept of “humanity” is therefore contested. Some populations are not treated as fully human by those who hold the greatest power of intervention. This raises an inevitable question: why Iran today and not Gaza yesterday?

Why the UN Charter rejects this logic

The drafters of the UN Charter anticipated precisely this type of abuse. Adolf Hitler justified his intervention in Czechoslovakia by claiming the need to protect the German population. Russia has used similar reasoning in Georgia and Ukraine. The United States did so in Iraq and now in Iran. None of these cases represented a sincere justification.

If a military power genuinely believes that the unlawful use of force is necessary to defend a higher moral value, it must accept the legal consequences of acting outside the law. Pretending to act legally without UN authorization merely turns humanitarian discourse into another instrument of political realism.

When announcing Saturday’s attacks, Trump explicitly stated that the objective was regime change. In his message to the Iranian people, he declared: “When we are finished, take control of your government. It will be yours to take.” Subsequently, Iranian state media reported that Supreme Leader Ayatollah Ali Khamenei had died in the joint attacks carried out by the United States and Israel.

To this framework must be added another dimension widely discussed in analyses and leaks: the perception that, in the initial phase, the CIA and Israel relied on a strategy of internal pressure aimed at regime change in Iran, based on the expectation that massive mobilizations would force the collapse of the political system. This assumption rested on the idea that large segments of Iranian society would respond to external calls to take to the streets and overthrow the regime. However, this reading reflected an insufficient understanding of the Iranian context, its political culture and its social dynamics, where foreign intervention tends to reinforce nationalist reflexes even among sectors critical of the government.

The outcome observed, according to images, official statements and regional reactions, points in the opposite direction to what proponents of this hypothesis expected. Instead of a social fracture leading to regime collapse, massive mobilizations motivated by anger and mourning have taken place, framed within a narrative of external aggression following the events that Iranian state media attribute to the death of Supreme Leader Ayatollah Ali Khamenei. Similar dynamics of protest and symbolic mobilization have also been observed in Iraq, Lebanon, Pakistan and other states, where the perception of aggression against Iran has acted as a political catalyst. Far from weakening the regional network associated with Tehran, these effects appear to have reinforced, at least in the short term, narrative cohesion and transnational mobilization around the confrontation.

Legal verdict

The attack carried out by the United States and Israel against Iran is illegal under international law. Media outlets that uncritically repeat the American narrative of preventive or humanitarian action fail to meet even the most basic standards of fact-checking.

Khalil Sayyad Hilario
Founder & CEO SAHCO Consulting
Madrid, March 3, 2026