Are the U.S. and Israeli Military Strikes on Iran Legal under International Law?

Are the U.S. and Israeli Military Strikes on Iran Legal under International Law?

By Debra DeLaet (Executive Director, Iowa United Nations Association)

On February 28, 2026, the United States and Israel launched joint military attacks on Iran, which killed Ayatollah Ali Khamenei, Iran’s supreme leader. One strike hit a girls’ elementary school in Minab, Iran, resulting in a death toll thus far of at least 175 people, presumably mostly children.

The U.S. and Israeli governments have offered various rationales for these attacks. The Trump administration justified previous limited attacks on Iran in June 2025 as necessary to hinder Iran’s development of nuclear capabilities. The February 2026 military operation came amidst ongoing negotiations over Iran’s nuclear program, which became necessary after the first Trump administration pulled out of a previously negotiated nuclear deal in 2018. In the recent airstrikes, President Trump expanded his rationale for military action as a measure intended to provoke regime change in Iran. Prime Minister Netanyahu, who likewise favors regime change, also points to Iran’s support of militant groups in the region as a justification for military strikes and has described the Iranian regime, which has provided material support to Hamas and Hezbollah, as an existential threat to Israel.

Do these rationales meet the legal requirements for the use of force under international law? The short answer is no. State sovereignty—the supreme authority of a state to govern itself as it sees fit—is the core principle of modern international law. Under this concept, states may not intervene in the internal affairs of other states. The principle of state sovereignty is enshrined in the UN Charter. Article 2 of the Charter specifies that the organization is based on the sovereign equality of its members and that member states are obligated to refrain from the threat or use of force in their relations with each other. A state’s right to sovereignty is not dependent on its form of government—non-democratic and democratic states alike have a fundamental right to sovereignty. Under this principle, a desire for regime change is not a legitimate rationale for the use of force under international law, even when human rights are at stake. Accordingly, UN Secretary General Antonia Guterres has condemned U.S. and Israeli airstrikes against Iran as violations of the UN Charter.

The logic of state sovereignty prioritizes international peace and stability over human rights not because human rights don’t matter under international law but because war poses an extreme threat to fundamental human rights. The UN Special Rapporteur on human rights in Iran, Mai Sato, condemned the U.S. and Israeli strikes as unlawful in the absence of a UN Security Council resolution. In her condemnation, she recognized that human rights conditions deteriorate in extreme ways during war.

What about the stated rationale of preventing Iran from acquiring nuclear weapons? The answer to this question is somewhat trickier. Article 51 of the UN Charter allows states the right of individual and collective self-defense:

Nothing in the present Charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.

Importantly, the language in Article 51 gives states a right to self-defense if an armed attack occurs. The possibility that Iran might acquire nuclear weapons in the future does not constitute an armed attack, indicating that this rationale does not meet the requirements for the legitimate use of force under international law.

Although UN law limits the right to self-defense to cases when an armed attack on a country has occurred, some international legal scholars argue that there is a right to preemptive self-defense under customary international law. Such a right, also referred to as anticipatory self-defense, would allow countries to respond proactively to imminent and inevitable threats rather than having to wait until an armed attack occurs. Notably, the Trump Administration described Iran’s nuclear program as an “imminent threat” to the United States. Israel’s government described its military actions as “preventative”. Their use of these terms suggests familiarity with discussions about preemptive self-defense in the scholarship on international law. However, Trump and Netanyahu’s use of these terms does not match the reality of any threat posed by Iran. Former U.S. intelligence officials have indicated that Iran does not pose immediate threats to the United States and that little evidence exists that Iran is actively trying to build nuclear weapons. In June 2025, the International Atomic Energy Agency affirmed that there is no evidence of a systematic Iranian program to produce a nuclear weapon.

Some scholars argue that just war theory offers states an ethical framework for using force outside of the parameters of UN law. However, the just war tradition is based on stringent criteria for a war to be considered ethical and legitimate. These criteria include not only just cause, the most well-known principle. A just war must also be waged as a last resort by a legitimate authority, be motivated by right intent, have a reasonable chance of success, be proportional to the original violence, and distinguish between combatants and non-combatants. It is unclear that the U.S. and Israeli airstrikes would fulfill all of these principles. For example, the fact that the airstrikes were conducted after all state parties had communicated their willingness to continue negotiations over Iran’s nuclear programs indicates that this use of force was not a last resort.

As this discussion shows, the U.S. and Israeli rationales for their airstrikes on Iran do not meet the legal threshold for the use of force under international law. In contrast, Iran’s counterattacks on Israel and against U.S. military bases in Bahrain, Kuwait, Qatar, and the United Arab Emirates might be considered a legal exercise of the right to self-defense under Article 51 the UN Charter given that they were launched in response to an armed attack on the territory and sovereign leadership of the country.

This still-unfolding conflict is likely to have major consequences for regional political stability and the global economy, particularly by disrupting oil and gas shipping lanes in the Strait of Hormuz. It remains to be seen how much the violence on all sides will escalate. Even if there is de-escalation, yet another use of unauthorized force by a major power further diminishes an international legal order that is already under siege.

Critics of the imperfect system of international law may be tempted to celebrate its decline. The constraints that international law places on the use of force even in the face of human rights atrocities are, to put it mildly, frustrating. Indeed, many world leaders, especially in the West, have condemned Iran’s counterattacks while failing to criticize the initial airstrikes by the United States and Iran. Given the brutality of the Iranian regime, this sentiment is understandable. But that does not make the use of force wise. When powerful states disregard the rules-based international order to justify the use of force based on their own values, interests, and ideologies, we can expect other actors—including major powers, less-powerful states, and militant groups—to do the same based on their own values, interests, and ideologies. These dynamics are likely to contribute to an increase in global political violence rather than peace, stability, and an expansion of human rights.