Extensive analysis already exists on the legality of the Israeli-U.S. attacks on Iran in June. This post concerns a different issue: the fact that both sides are united in the view that international law is the standard against which to judge any inter-state use of force. While a seemingly obvious point, it turns out to be no minor shared assumption at a time when the rule of law in general is under threat.
Geoffrey Corn and Orde Kittrie are scholars who defend the legality of Israel’s attacks in their June 18 analysis published in the Rule of Law Post. I reach the opposite conclusion here, in agreement with many others. I will explain my position below but wish first to emphasize the contribution Corn, Kittrie, and others make in turning to international law and not simply assuming might makes right. Even in democracies, governments increasingly view law as an obstacle around which to maneuver rather than the foundation of and reason for their existence.
With the end of the Cold War, U.S. presidents have increasingly sought ways around international law on the use of force or ignored it altogether. This attitude toward law began to migrate home. Why bother with law on domestic issues at home, including the deployment of U.S. Armed Forces, if troops are ordered to act in disregard of ancient legal-normative principles abroad? This attitude was perfectly expressed by John Bolton, President Trump’s former national security adviser, when he called international law “an academic sham” in the context of the unlawful use of force in the 1999 Kosovo Crisis. Today, it is no longer enough to assess compliance with particular international rules and principles. Legal experts find themselves having to defend the essential role of law in governing governmental action across the board, both internationally and domestically.
One way that some scholars have sought to retain the relevance of international law for governments is to take a flexible approach to legal interpretation. Rather than risk policymakers ignoring the law, they have used creative arguments to find a justification. In my view, this approach is part of the reason law is in crisis today. With so many compromises having been made, law is reduced to non-binding guidelines. My own approach is to follow standard international legal method. The rules on treaty interpretation, for example, are codified in the Vienna Convention on the Law of Treaties and require in Article 31(1) that treaties “shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose.” The United Nations Charter Article 2(4) is the first relevant treaty provision for interpretation and application in this case. It is a comprehensive prohibition on the use of force with only two express limitations: The UN Security Council may authorize force when necessary to respond to threats to the peace, breaches of the peace, or acts of aggression. (UN Charter Articles 39-42.) States may also resort to force in individual and collective self-defense if, in the terms of Article 51, “an armed attack occurs,” until the Security Council can act. All action in self-defense must be reported to the Council.
General principles of international law provide additional restrictions. The principle of necessity mandates that even when a lawful basis for resort to force in self-defense exists, the force must be a last resort and must have a reasonable chance of accomplishing the lawful aim of self-defense. The principle of proportionality requires that the response be equivalent to the wrongful act. In the Oil Platforms Case, the International Court of Justice (ICJ) found the U.S. destruction of Iranian oil platforms to be disproportionate to the violations of Article 2(4) alleged by the United States in the case. “Collective” self-defense means any state may join with a state that has been attacked to assist in its defense. The United States joined Israel in attacking Iran. Because Israel had no right to resort to force against Iran, neither did the United States.
To be sure, Iran also violated international law regarding its response to the Israeli attacks. Iran had a basis for resort to force in Article 51 because of unlawful armed attacks against it. However, Iran did not satisfy the principle of necessity with its counterattacks because it had no reasonable expectation that it would enhance its own security with such a response. Iran’s attacks, in my estimation, were mere punitive reprisals, not a use of force in self-defense. Armed reprisals are clearly prohibited under international law.
Corn and Kittrie do not start with Article 2(4). They assert that an armed conflict between Israel and Iran was already underway when Israel attacked. It was not a first use of force prohibited by the Charter. The only relevant legal questions fell under the jus in bello (international humanitarian law or IHL), not jus ad bellum.Israel itself hinted at something like this in the letter it was required to send to the Security Council under Article 51 notifying the Council of its actions and the justification, therefore. Yet there appears to be a contradiction here, because letters to the Security Council are required to explain a first resort to force in self-defense. Israel was not required to send a letter if the attacks occurred during an armed conflict already underway.
In fact, under the definition in international law, no armed conflict was underway between Israel and Iran when Israel attacked. The International Law Association’s Committee on the Use of Force provided extensive authority that “as a matter of customary international law a situation of armed conflict depends on the satisfaction of two essential minimum criteria, namely: a. the existence of organized armed groups [and] b. engage[ment] in fighting of some intensity.” The shortest period of fighting the Committee found that qualified as an armed conflict was an engagement between Argentina’s armed forces and organized, armed militants that resulted in casualties and property destruction during a 30-hour period. The Inter-American Commission on Human Rights made this determination stressing that the critical factor was the intensity of the fighting.
Israel and Iran had last exchanged air attacks in April 2024. They were not engaged in intense exchange of fighting on June 13, when Israel initiated its strikes against Iran’s nuclear weapons program. This was not a close case, but if it were, the presumption is in support of peace, which is the “normal situation.” Despite its all too frequent occurrence, war is legally “the abnormal.”
Few dispute this finding, but some argue that because Iran’s “proxies” were fighting Israel on June 13, Israel and Iran were at war. They point to Hamas militants in Gaza and Houthi forces in Yemen. It is true that intense armed fighting was occurring on June 13 in Gaza, and exchanges of missile attacks had occurred throughout May between Israel and the Houthis. These facts are not enough, however, under international law to determine that Iran was a party to either conflict. Iran apparently had no forces of its own involved in fighting, though Iran has provided military assistance to Hamas and the Houthis in the past. Even if it was actively supplying assistance during fighting on June 13, assistance does not amount to participation in armed conflict. The United States and other NATO members supply considerable assistance to Ukraine but do not consider themselves parties to the armed conflict with Russia.
The ICJ has set a high bar to finding that provision of assistance amounts to an armed attack, let alone participation in the actual intense fighting of an armed conflict. The United States benefitted from this finding in view of the extensive military assistance it provided to the “Contras” fighting the Nicaraguan government in the 1980s. The ICJ found the United States violated the principle of non-intervention but was not a co-party with the Contras or even responsible for their grave human rights violations. Iran has violated significant principles of international law by supplying military assistance to non-state actor armed groups. At the time of June 13, however, it was not participating with them in an armed conflict against Israel.
Even if Iran was using force directly against Israel as part of the Gaza and Houthi conflicts, bombing Iran’s nuclear program would not meet either the jus ad bellum or jus in bello necessity requirements. As discussed above, under the jus ad bellum, even with a lawful basis under Article 51, the counterattack must aim at achieving security against the attacker. Under jus in bello or customary IHL, necessity as restated in Additional Protocol I Article 52(2), means “military objectives are limited to those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage.” Bombing the Iranian sites associated with its nuclear program provided no definite military advantage at the time in Gaza and Yemen.
Michael Schmitt is another who attempts to defend the Israeli attacks. He does not argue for finding an on-going armed conflict. Instead, he substitutes his own method of interpretation for the Vienna Convention. He calls his method “adaptive interpretation” and applies it to Article 51 to find a state is justified in attacking in the total absence of an armed attack occurring if the attacking state believes the target state’s leaders intend to attack in the future and are acquiring the means to attack, and the attacker believes it is looking at “the last window of opportunity” to prevent the attainment of that capacity.
This effort at rewriting the Charter comes despite the evidence that Iran had made no decision to produce a weapon. It was enriching uranium far beyond the requirement for power generation, which provided a bargaining chip in negotiations.
Neither war nor deterrence theory is the answer to the grave threat posed by nuclear weapons. Treaties are. Despite the 12-day war and immense fire power Iran’s program has reportedly been set back by only months. The Nuclear Non-Proliferation Treaty has succeeded in limiting possession of nuclear weapons to nine states. Libya and Ukraine gave up weapons under treaty arrangements. North Korea and Iran were on the path to ending programs but did not receive the benefits promised. It was President Trump who reimposed sanctions on Iran in defiance of the Security Council and the requirements to lift sanctions in the 2015 Nuclear Agreement. In 2025, he was ready to return to the negotiating table when Israel undertook its attacks. The world will need to eliminate nuclear weapons through treaties even more urgently with the emergence of AI programmed for pre-emptive use of force. The risk of losing control of the systems operating nuclear weapons to AI is real and the negative consequences potentially catastrophic. If AI can be programmed for lawful defense, however, the world gains an invaluable tool for protection. Israel’s Iron Dome is the model, but it has been undeveloped likely owing to too much focus on pre-emptive, offensive uses of force.
Over time, U.S. leaders have come to see the United States as above the law, the same law they continue to insist is binding on other states. The Clinton administration decided to attack Serbia during the Kosovo Crisis in clear violation of Charter Article 2(4). When the British Foreign Minister said his lawyers had concerns about this, Secretary of State Madeline Albright is said to have responded, “Get new lawyers!” The British legal adviser Elisabeth Wilmshurst stands out for the fact she resigned her government position when the United Kingdom joined with the United States in invading Iraq in 2003 in defiance of Article 2(4). Other lawyers did not. Instead, the flexible answers continued on Libya in 2011, on reprisal attacks on Syria in 2017 and 2018, and on countering terrorism. Some flexible answers were provided out of concern that presidents and prime ministers would otherwise abandon the law entirely. Like defense lawyers in criminal cases, lawyers can always find some form of justification for the use of force when the president wants to engage in it.
Contempt has been bred through the false perception there is always an argument around the law. It is time to correct the record. In my recent article, What Remains of Law Against War, I discuss how to build up the gravitational attraction to compliance with the law. The approach begins with clear, accurate, solid statements of what the law actually mandates. Regardless of why a legal expert took the flexible or defense-lawyer approach in the past, they need to be objective supporters of the law that is from this point forward—from law on the use of force to government contracts. It is imperative to speak truth to power, and that means the whole truth.
At the end of the day, over 1,000 people were killed and many more than that injured across Iran and Israel for little or no gain. Admittedly, the Trump administration handles treaties so cavalierly that any party to future treaties involving the United States will require extraordinary provisions to ensure compliance by all sides. Hopefully, resourceful international lawyers can find a way to convince political leaders to support compliance with the plain meaning of treaties between the United States and other nations to rebuild trust and to enable the treaty to again be the workhorse of international relations. Treaties and the law in general are the most promising foundation for international peace and security.
Mary Ellen O’Connell is the Robert and Marion Short Professor of Law and Professor of International Peace Studies—Kroc Institute at the University of Notre Dame. Her full bio is available here.
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