Strikes on Iran’s Nuclear Program: A Violation of International Law?

Following the massive airstrikes on Iranian nuclear facilities—carried out with U.S. support for Israel—a longstanding legal debate has gained new urgency: Were core principles of international law violated, or can the attack be justified under existing legal frameworks?

At the heart of the issue is Article 51 of the UN Charter, which allows for the right of self-defense—both individual and collective. This was the key argument invoked by U.S. Ambassador to the UN, Dorothy Shea, during Sunday’s emergency session of the Security Council. Two conditions are essential for such a justification: Israel must have requested U.S. assistance—something confirmed through multiple diplomatic channels—and Israel must be able to invoke its own right to self-defense.

This brings renewed focus to an old debate: How far does the internationally recognized right to self-defense extend? Article 51 permits the use of force only “if an armed attack occurs.” Based on that narrow wording, many legal scholars reject the notion of preemptive self-defense altogether. Yet in practice, few states today would accept the idea that they must wait until after a nuclear strike to respond. This has led to an evolving interpretation of Article 51 that allows for preventive strikes—provided an attack is deemed “imminent.”

But what does “imminent” actually mean? Is it simply a matter of timing—or should factors such as the scale of the threat, the clarity of intent, and the consequences of inaction also be considered? Applied to the Iranian case: Must Israel wait until Tehran has built and authorized the use of a nuclear bomb, or does the existential nature of the threat warrant broader discretion?

This is precisely the logic put forward by Israeli Foreign Minister Gideon Saar in a letter to the UN Security Council. He argued that Iran has repeatedly threatened Israel with annihilation and is now on the brink of acquiring nuclear weapons. Saar described the current situation as the “last window of opportunity,” asserting that all diplomatic efforts had failed. His phrasing echoes the legal standard proposed by U.S. scholar Michael Schmitt in the aftermath of 9/11, which holds that in the case of weapons of mass destruction, states cannot be expected to wait until the very last moment. Instead, the decisive criterion should be whether there remains any realistic chance to act in time.

Schmitt was among the first prominent legal experts last week to publicly back Israel’s position. His argument: If a state openly threatens another with annihilation, it must expect to be taken at its word. The burden of proof, he said, should fall on the aggressor—not the potential victim.

But the biggest obstacle to any legal assessment remains the uncertainty of the facts. While Israel considers the threat immediate, many observers view Tehran’s rhetoric as saber-rattling—especially given Israel’s own nuclear second-strike capabilities. Another key question is whether this really was the last opportunity to halt Iran’s nuclear program—or merely a politically convenient one. Though the Trump-era diplomatic deadline had lapsed, further negotiations were reportedly in the pipeline. Israel claims Iran has used diplomacy merely to buy time while continuing its nuclear activities in the background.

By contrast, several U.S. intelligence agencies have repeatedly expressed doubts that Tehran has made a final decision to build a bomb. This raises a broader legal question: How should decisions based on uncertain or contradictory intelligence be evaluated under international law—and who bears the risk of getting that judgment wrong?

One final factor is also key to determining the legality of the strikes: the response of the international community. State practice is a central element in the interpretation of international norms. While most Anglo-American countries have long favored a broad interpretation of self-defense, Germany has so far avoided a clear legal position—though it continues to emphasize Israel’s right to defend itself, as echoed in the recent G7 statement.