ToplineMore than 100 international law experts signed an open letter warning American military strikes on Iran violate international law and could amount to war crimes, as President Donald Trump threatened to destroy Iran’s civilian infrastructure unless the country’s leaders agree to his demands. Concrete and rebar dangle from a damaged B1 bridge, a day after it was destroyed by a U.S. airstrike, in Karaj, Iran.Getty ImagesKey FactsThe open letter was signed by law professors and experts from ⁠Harvard, Yale, Stanford, Columbia and other U.S. universities, along with former government legal advisors.The letter called the conflict a “clear violation of the United Nations Charter” and criticized the conduct of U.S. forces and “statements made by senior government officials.”Trump’s actions have raised “serious concerns about violations of international human rights law and international humanitarian law, including potential war crimes,” the letter added.Remarks made by Defense Secretary Pete Hegseth describing rules of military engagement as “stupid” were also called out in the letter, as well as his demands for “lethality” over “legality.”The experts warned Hegseth’s “gloves off” approach was decimating the U.S. military systems that are in place to reduce hard on civilians during a conflict.What Did Trump Say About Targeting Iran’s Infrastructure?In a post on Truth Social on Thursday night, Trump wrote: “Our Military, the greatest and most powerful (by far!) anywhere in the World, hasn’t even started destroying what’s left in Iran. Bridges next, then Electric Power Plants! New Regime leadership knows what has to be done, and has to be done, FAST!” Under international law, attacks on civilian infrastructure are considered a war crime. What To Watch ForNATO Secretary-General Mark Rutte is scheduled to visit Washington, D.C. next week, amid Trump’s threats to pull the U.S. out of the Western military alliance. The president has expressed frustration about other NATO members’ reticence to help the U.S. in the conflict. Rutte himself has reportedly faced some pushback from European leaders over his comments about the Iran war. Last month, the NATO chief said Trump was attacking Iran to “make the whole world safe” and “iIt’s only logical that European countries take a couple of weeks to come together” and “answer the president’s call, to make sure that we secure the free sailing through the Strait of Hormuz.”Crucial QuoteLast month, United Nations Secretary-General António Guterres decried the attack on civilian infrastructure both by Iran and the U.S.-Israeli coalition and said: “If there are attacks either on Iran or from Iran on energy infrastructure, I think that there are reasonable grounds to think that they might constitute a war crime.”Key BackgroundTrump has repeatedly threatened to blow up Iran’s power plants, oil wells, and other civilian infrastructure if it failed to comply with his demand to reopen the Strait of Hormuz and agree to the U.S.’s terms to end the war. A threat issued by Trump on Monday also mentioned Iran’s water desalination plants as potential targets, which experts have warned could cause a humanitarian crisis. On Thursday, the president shared a clip on Truth Social showing a U.S. strike on a newly constructed Iranian bridge connecting the city of Karaj with the capital Tehran. On the opening day of the U.S. strikes, 175 people, mostly children at a girls' school, were killed in the city of Minab in a missile strike that experts believe was carried out by the U.S. military.