June 23, 2025

To the Editor:

White House claims about the supposed success of US bombing in Iran are highly uncertain, but there is no doubt that unprovoked US and Israeli military strikes against Iran are a direct violation of international law. Article 2, (4) of the UN Charter prohibits states from using military force against other states without the approval of the Security Council, except for self-defense. States may use force to defend themselves when they are under attack by an aggressor, as Ukraine is doing, but that is not the case in this instance. Israel was not under attack when it began military action nearly two weeks ago. Iran did not use force first or threaten to do so.

The United States claims that its attack against Iran is justified as a preventive measure to stop the Tehran government from developing nuclear weapons. Israel has used similar arguments, claiming that military action is necessary to avoid a future Iranian nuclear attack.

The principle of preventive war in international law is not widely recognized, and if applied must be strictly conditioned. Preemptive action may be permissible if a country is responding to an imminent threat of attack, according to historical standards, but only if the threat of aggression is “instant, overwhelming, leaving no choice of means, and no moment for deliberation.”

These conditions clearly do not exist in reference to Iran, which has accelerated its enrichment program but does not yet have a nuclear weapon. Prior to the US attack, the White House claimed that Iran could produce a bomb “within a couple of weeks.” Mossad, the Israeli intelligence agency, asserted that Iran would need only 15 days to achieve a nuclear weapon. US intelligence agencies assessed in March, however, that Iran had not yet made a decision to build a nuclear weapon.

Iran’s stockpile of higher enriched uranium has been growing at an alarming rate, prompting the International Atomic Energy Agency to declare the country in breach of its nonproliferation obligations. Enriched uranium per se is not an immediate weapons threat. As Kelsey Davenport of the Arms Control Association has observed, if Iranian officials decided to create a bomb, it would take up to a year to convert its enriched uranium into metallic form and create an explosive device. The threat of an Iranian bomb is serious but not “instant” or “overwhelming.”

The preemption justification also fails because alternative means for addressing the threat have been available and were actively underway. Tehran was engaged in negotiations with Washington to restrict its nuclear program when the Israeli attacks began. As the US threatened to bomb, Iran sent urgent signals indicating its willingness to return to the bargaining table. Deliberations for possible diplomatic solutions were underway as the bombs began to fall.

The use of force is not an effective means of preventing nuclear proliferation. On the contrary, the current Israeli and US armed assault could create the very danger it is intended to prevent. Senior US intelligence officials warned before the strikes began that attacking Iran’s nuclear sites would likely shift Tehran toward producing a bomb. On Monday, June 17, soon after the first Israeli strikes, the Iranian parliament introduced a bill that—if passed—could see Iran withdraw from the Nuclear Non-Proliferation Treaty. The humiliation of being attacked by the US and Israel may convince Iranians that acquiring nuclear weapons capability is necessary to deter similar aggression in the future.

Most nonproliferation successes have been the result of negotiated agreements, not the use of force. South Africa, Libya, Argentina, Brazil, Ukraine, Kazakhstan, and other states gave up the bomb or terminated nuclear development through negotiated agreements that provided security assurances, sanctions relief, and the promise of global economic integration.

In 2015 Iran negotiated an agreement with the US, the UK, Russia, China, France, and Germany for major reductions in its nuclear program, including unprecedented levels of intrusive verification. Iran was implementing the deal fully when the first Trump administration reneged on the agreement in 2018 and reimposed coercive sanctions. This prompted Iran to resume and intensify uranium enrichment. The US renunciation of the 2015 agreement set in motion a negative action-reaction cycle that has led to the current crisis.

US and Israeli attacks certainly caused severe damage to Iran’s nuclear facilities. US bombs reportedly hit uranium enrichment sites in hardened, subterranean facilities. The President claims that Iran’s nuclear program is “obliterated,” but that is extremely doubtful. Nuclear materials were being removed from production sites prior to the bombing. James Acton observes that Iran retains a large stockpile of centrifuge components. He estimates Iran could reconstitute its nuclear program rapidly, perhaps within a year. US and Israel bombing raids can destroy physical facilities, but they cannot eliminate the breadth of scientific and technical knowledge acquired in Iran during decades of advanced nuclear development. If Iran decides to build a bomb it will find a way.

Israel’s lawless military attacks against Iran come in the context of the Netanyahu government’s violations of international law in Gaza. Israel was justified in defending itself against Hamas’ terrorist attacks on October 7, 2023, but the military occupation and often indiscriminate use of force in Gaza have taken the lives of more than 50,000 Palestinians, including thousands of civilians. The homes and livelihoods of more than a million people have been devastated.

The International Criminal Court declared in July 2024 that Israel’s continued occupation of Gaza was unlawful. Human Rights Watch has described Israel’s denial of humanitarian assistance to Palestinians in Gaza as a flagrant violation of international humanitarian law. Former Israeli Prime Minister Ehud Olmert has written that Israel is committing war crimes in Gaza.

The US has turned Israel’s illegal war into an American war. For many in Washington the use of force against Iran is seen as an act of support for Israel, but the conflict is leading to greater isolation for Israel and the loss of potential allies among nations in the region.

The United States is and always has been a friend of Israel, but the commitment to support a friend should not extend to complicity in illegal acts. When a partner goes astray, a friend steps in to help them get back on course. The United States has failed in that duty, doubling down on the illegal use of force and launching a war that is likely to have catastrophic consequences for Israel and the Middle East region.

David Cortright is a professor emeritus at Notre Dame’s Keough School of Global Affairs and a visiting scholar at Cornell’s Reppy Institute for Peace and Conflict Studies. He is the author of more than 20 books on peace and nuclear disarmament issues.