On Thursday, April 2 — one day after President Trump's primetime address in which he vowed to hit Iran "extremely hard over the next two to three weeks" — more than 100 U.S.-based international law experts published an open letter calling the entire Iran war campaign a "clear violation of the United Nations Charter." The letter, published by Just Security, is signed by senior professors, leaders of prominent international law associations, former government legal advisors, military law experts, and former Judge Advocates General (JAGs) — the lawyers who advise U.S. military commanders on the laws of war. The signatories said the conduct of the war raises "serious concerns about violations of international humanitarian law, including potential war crimes." The letter was reported by the New York Times, Common Dreams, and Alternet. This is not a political statement. It is a legal argument, made by people whose careers are dedicated to the law that governs armed conflict — and it applies to Iran's conduct as well as the United States'.
The Core Legal Argument: No UN Charter Authorization
The letter's central argument rests on the United Nations Charter's rules governing when states may legally use military force. Under the Charter, force against another state is permitted only in two circumstances: in self-defense against an actual or imminent armed attack, or when authorized by the UN Security Council. Neither condition, the letter argues, was met on February 28, 2026, when the United States and Israel launched strikes on Iran.
The letter states directly: "The Security Council did not authorize the attack. Iran did not attack Israel or the United States. Despite the Trump administration's varied and sometimes conflicting claims to the contrary, there is no evidence that Iran posed an imminent threat that could ground a self-defense claim."
The Trump administration has offered several different justifications for the war at different points — ranging from Iran's nuclear program to claims of imminent attack to broader regional security arguments — which the letter characterizes as "varied and sometimes conflicting." The NPR article by Scott Detrow interviewing Gabor Rona, who directs the Law and Armed Conflict Project at Cardozo Law School and previously served as a legal adviser to the Red Cross, provides additional context on why the self-defense justification is legally contested.
The Conduct Concerns: "No Quarter, No Mercy"
Beyond the decision to go to war, the letter raises four categories of concern about how the war has been fought. It addresses jus ad bellum (the decision to go to war), jus in bello (conduct of hostilities), rhetoric and threats from senior officials, and the "decimation of civilian harm mitigation structures" inside the Department of Defense.
On official rhetoric, the letter specifically highlights Defense Secretary Pete Hegseth's public statements. Common Dreams, citing source reporting on Hegseth's statements, documents that Hegseth described the rules governing military engagement as "stupid" and said the U.S. was seeking to prioritize "maximum lethality, not tepid legality." The letter also highlights Hegseth's mid-March pledge to give "no quarter, no mercy for our enemies" — language the letter describes as "especially prohibited" under international law and as a violation of the Department of Defense's own war manual. The phrase "no quarter" has a specific meaning in the law of armed conflict: it refers to a refusal to take prisoners, which is explicitly prohibited under the Geneva Conventions.
Trump's own statements are also cited. The letter notes that Trump has said explicitly that he doesn't "need international law," according to Common Dreams' reporting on the letter's contents.
The Desalination Threat: What the Law Actually Says
One of the sharpest specific concerns in the emerging legal debate involves Trump's threats to destroy Iranian desalination plants. On NPR's April 1 broadcast, Gabor Rona addressed this directly when host Scott Detrow asked whether attacking a desalination plant would constitute a war crime.
Rona's answer, quoted verbatim from the NPR transcript: "Absolutely, Scott, both under international law and U.S. law. We have a War Crimes Act that prohibits precisely this kind of thing. It would also be a violation of laws against terrorism. It's prohibited to engage in attacks in armed conflict where the primary purpose is to spread terror among the civilian population. If you're targeting a desalination plant, then that would be an act of terrorism."
The White House press secretary Karoline Leavitt, asked about Trump's comments on targeting civilian infrastructure, said at a briefing: "Of course, this administration and the United States Armed Forces will always act within the confines of the law. But with respect to achieving the full objectives of Operation Epic Fury, President Trump is going to move forward unabated." That quote is reported in the NPR transcript.
Rona further noted that the law does not require intent to trigger war crimes liability: "Even though one might have been mistaken and the other intentional, under U.S. law, both intentional and mistaken attacks that aren't pursuant to due diligence can be war crimes." He also stated: "one of the things that's well settled in international law is that a violation by one side does not justify a violation on the other side" — addressing the fact that Iran has also struck civilian infrastructure across the Gulf.
The Civilian Cost: What the Letter Documents
The Just Security letter anchors its concerns in documented harm. It states that the war "is costing U.S. taxpayers between $1-2 billion each day," citing a Detroit News report on war funding. It states the war has "resulted in the loss of hundreds of civilian lives across the Middle East" and is causing "serious environmental and economic harms" — citing reporting on toxic clouds from bombings of oil facilities in Tehran and a Climate and Community Institute analysis of emissions from Iran strikes.
The letter is explicit that its concerns apply to all parties: "We remain concerned about the risk of atrocities across the region including the continuing risks posed by the Iranian government to Iranians through violent crackdowns on dissent, and to civilians across the Middle East through Iran's ongoing unlawful strikes on civilian infrastructure using explosive weapons in densely populated areas." The letter is not a defense of Iran — it is an application of the same legal standards to all belligerents.
Who Signed It and Why It Matters
The signatories are not fringe academics. The letter was published by Just Security, a peer-reviewed forum on security law affiliated with the Reiss Center on Law and Security at NYU School of Law. The list includes senior law professors, leaders of the International Law Association's American Branch, former government legal advisors, military law experts, and former JAGs — the uniformed lawyers who have advised U.S. military commanders on rules of engagement in every major U.S. conflict since Vietnam.
The involvement of former JAGs is particularly significant. These are individuals who spent careers working within the U.S. military legal system, advising commanders on what is and is not legally permissible under the laws of armed conflict. Their concern about Hegseth's "no quarter" rhetoric and his characterization of rules of engagement as "stupid" carries institutional weight that purely civilian legal criticism does not.
The New York Times noted Thursday that the letter was among the developments covered in its Iran war live blog, placing it alongside the Macron criticism of Trump's "shifting goals" and the UK-led Hormuz summit — framing the legal challenge as part of the broader international pressure building against the U.S. campaign's management, if not its existence.
What Happens to War Crimes Allegations
The practical question of accountability is the one Gabor Rona was asked to address on NPR, and his answer is blunt: accountability for potential U.S. war crimes in Iran would have to come through U.S. domestic law, because the United States is not a signatory to the Rome Statute and thus not subject to ICC jurisdiction. The U.S. War Crimes Act, 18 U.S.C. § 2441, does provide a domestic legal mechanism — but prosecution under it would require a Justice Department willing to bring charges, which analysts widely assess as unlikely under the current administration.
The letter itself does not demand prosecution. It demands acknowledgment: that the United States is bound by international law including the UN Charter, and that conduct inconsistent with that law has occurred and is ongoing. Its publication is a legal record, not a legal proceeding.
One hundred scholars who have spent their careers studying the laws of war have said, in writing: the war is illegal, the rhetoric is alarming, and the destruction of civilian harm mitigation structures inside the Pentagon is dangerous. That document exists now. What happens with it is a separate question.