U.S. Attacks on Iran
Defying the Law to Follow a Theory
Israel and the United States attacked Iran in mid-June 2025 with the aim of ending its nuclear program. Iran counter-attacked. While some world leaders justified what Israel and the U.S. were doing, they did so in line with political deterrence theory, not the plain terms of the United Nations Charter. The lawful use of force in self-defense depends on an armed attack occurring. Concerns over nuclear weapons are to be resolved through treaties and negotiations. Honoring deterrence theory over the law is undermining the surest path to peace.
The casualties
On 13 June, Israel began air attacks on Iranian nuclear sites and military targets. Israel also carried out over a dozen targeted killings of scientists and military figures. Iran retaliated, conducting air attacks against Israel. About ten days later, the United States joined Israel, dropping 14 “bunker buster” bombs and launching multiple cruise missiles against three sites. President Trump debated in public for days about whether he would order the attack, while making no move to involve Congress as contemplated in the Constitution and War Powers Act.
Following the U.S. attack, Iran retaliated again. It struck an American airbase in Qatar after issuing a warning about its intentions. No casualties were reported. Thousands of people have died or been injured, however, between Israel’s first strike and an apparent ceasefire. The extent of destruction to the built and natural environment is unknown. Controversy rages over whether the combined Israeli-U.S. military operations set back Iran’s nuclear program in any meaningful way.
International law has also been a casualty. NATO Secretary General Mark Rutte, declared on the eve of President Trump’s visit to the NATO Summit in The Hague on June 24 that the U.S.’s attacks “did not break international law”. Britain’s Prime Minister Starmer praised the attacks. Germany’s Chancellor Merz went farther, saying there was “no reason to criticize” Israel’s or the U.S.’s actions. Rutte’s assessment likely had little weightit was just more flattery aimed at Trump, along with calling him “the daddy”. Starmer’s position is more surprising, but Merz’s is troubling and needs to be countered. Germany’s commitment to international law in its Basic Law and foreign policy since the end of World War II has played an important role in upholding the ideal of law over force. The urgent goal of improving compliance with international law generally, and the law of peace, in particular, depends on accurately applying law to facts, recognizing violations, and criticizing violators.
The prohibition on the use of force
Accurate application begins with the most basic general principle: the prohibition on the use of force in United Nations Charter Article 2(4). Article 2(4) is a comprehensive ban on all resort to force against another state. It is a peremptory norm, meaning it does not diminish regardless of how often it is defied, or attempts are made to replace it with new treaties, rules of customary law, or new interpretations. Article 2(4) can expand to outlaw more force but never contract to prohibit less. These features of the prohibition are shared by all peremptory norms, including the bans on torture, genocide, slavery, and apartheid. No one can imagine shrinking the prohibition on genocide. The same holds for resort to force. If a state has concerns about a nuclear weapons program, terrorism, threats to territorial integrity, instability or crime emanating from another state, the option provided by the Charter is to turn to the UN Security Council or to peaceful alternatives. Alternatives to force exist for all of these challenges. Hard experience shows that following the law and using these options is far more effective over time than resort to unlawful force. The invasion of Iraq in 2003 is a prime example of hard experience.
The Charter has one other express limitation on Article 2(4). Article 51 provides a “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. …” Article 51 sets a high bar in order to maintain the supremacy of both Article 2(4) and the Security Council. The right provided is to halt and repel attacks that are occurring. It is not a right to preempt an attack not in evidence. Without a basis in Article 51, resort to force by Israel and the U.S. violated Article 2(4).
Iran’s case
Iran’s case is more complicated. It was the victim of an armed attack and responded in a timely way with counterforce. However, in addition to the provisions of the Charter, general principles of international law, including necessity and proportionality, also apply. General principles are just as durable as peremptory norms. Every major judgment of the International Court of Justice on the use of inter-state force cites them. Necessity means that in addition to a lawful basis for resort to force under the Charter, force must be a last resort and must at the outset have a reasonable chance of accomplishing the lawful purpose for which it is being used. Even then, the responsive force must be proportionate, which means it must be equivalent to the attack that gives rise to the right of self-defense. If a state unlawfully initiates force with three missile strikes, sending an invading army to occupy in response is disproportionate.
Proportionality was not the main legal flaw in Iran’s responses. That was its failure to meet the necessity requirement. Iran’s acted on the basis of self-defense, but it could not achieve its defensive purpose the strikes it carried out. Many were on civilians or were repelled by Israel’s shield system. The attack on Qatar was all show, not protection. It was part of the deterrence game—attempting to send a message of strength and resolve. There is no right to use force to punish, seek revenge, send a message, or somehow seek to “deter” future attacks. That is not how the law works. Deterrence is an unproven theory of political science, which carries far too much influence over governments and their security policies.
Ongoing armed conflict and imminence
Two arguments are around attempting to justify the Israel-U.S. attacks. One is that Israel is in an ongoing armed conflict with Iran because of Iran’s support for armed militias or because of the tit-for-tat exchange of attacks months ago. These intermittent events, however, do not meet the definition of armed conflict in international law. An armed conflict is the intense exchange of fighting by two or more armed groups that lasts for a day or more. Even if these conditions were met in the past, within a reasonable period of their ending, so does the armed conflict. What counts as “reasonable” needs to be assessed in light of the presumption of peace. Indeed, any doubt about facts needs to be resolved in line with the prohibition of force. In the case of Israel and Iran months have passed since the last exchange of air attacks. Israel’s one-sided assassinations are not the sort of violence that constitutes armed conflict in the first place. Intermittent attacks by armed militias in the region need to pass a further test of being attributable to Iran but even passing that test, terrorism – like assassination – is a one-sided act of violence, not an exchange. Terrorism is properly classified as crime, not an armed conflict.
There is an even less persuasive variation on the on-going armed conflict argument. It holds that Israel has been in an armed conflict since its founding with any state that has attacked it until a peace treaty is agreed. Again, this argument does not meet the international law test of what constitutes an armed conflict.
The second argument that is around involves a new interpretation of Article 51. It replaces the words “if an armed attack occurs” is with if an attack is “imminent” or if a possible future attack poses a very great danger, then force is lawful in self-defense. Treaty interpretation, however, starts from the plain meaning of its words; in this case those words are “if an armed attack occurs.” The negotiating history is plain that the drafters meant what Article 51 says. The first authors writing on its meaning all emphasized the actual armed attack requirement. It is a right to “halt and repel” an armed attack. The ICJ called armed attack the “sine qua non” of the law of self-defense. There must be evidence of an attack occurring regardless of the gravity of the supposed future threat involved. If evidence exists the attack is happening, defense may begin on the territory of the state responsible if necessary and appropriate. Treaties are the way to end weapons programs, not war.
The Cold War deterrence playbook
The three governments involved in this tragic conflict are not following the Charter, they are following the old, Cold War deterrence playbook. It is the book that NATO follows, and it is making the world an even more dangerous place than the Cold War was. That much is clear. The puzzle is why lawyers would reinterpret the Charter to provide legal cover to governments pursuing deterrence, not lawful self-defense. .
At the end of the Cold War, Louis Henkin, one of the greatest international lawyers of the 20th century saw the emerging temptation to manipulate the words of the Charter to suit the sole military superpower of the time. He said this in response:
“[I]t is important that Charter norms – which go to the heart of international order and implicate war and peace in the nuclear age – be clear, sharp, and comprehensive; as independent as possible of judgments of degree and of issues of fact; as invulnerable as can be to self-serving interpretations and to temptations to conceal, distort, or mischaracterize events. Extending the meaning of “armed attack” and of “self-defense,” multiplying exceptions to the prohibition on the use of force and the occasions that would permit military intervention, would undermine the law of the Charter and the international order established in the wake of world war.”
He echoed the earlier warnings of another international law great, Hersch Lauterpacht, on the negative impact of realist theories like deterrence on international law. In the age of rising geo-political competition, the importance of the rule of law at home and abroad has never been greater. If Israel, the United States, and Iran want peace, they need to practice it—the law of the Charter and the alternatives to force provide the mandate and the means.