(Center for Ethics and the Rule of Law-University of Pennsylvania) Geoffrey Corn and Orde F. Kittrie - Israel's attacks on Iran's nuclear weapons program are lawful. Several commentators contend that Israel's attack is illegal since Israel was not responding to an "imminent" nuclear attack by Iran. But this argument overlooks a critical legal principle: When two countries are already in a state of armed conflict, there is no requirement to wait for "the next attack" to be imminent. The armed conflict between Iran and Israel has been ongoing since at least April 13-14, 2024, when Iran fired over 300 drones and missiles at Israel and, in the view of some experts, even prior to this date as the result of attacks against Israel by Iran's main proxy, Hizbullah. Then, on Oct. 1, 2024, Iran launched over 180 missiles at Israel. While an armed conflict continues, there is no requirement to justify every attack against the enemy through the pre-war imminence test. With Iran already engaged in ongoing conflict with Israel, international law did not require Israel to wait to take military action until just before Iran either launched a nuclear missile against Israel or otherwise fired its proverbial next shot. Instead, it was legal, as well as logical, that Israel attack the enemy's most dangerous weapon system - Iran's nuclear weapons program. Brian J. Egan, while serving as State Department legal adviser under President Obama, explained that, "In the view of the United States, once a State has lawfully resorted to force in self-defense against a particular armed group following an actual or imminent armed attack by that group, it is not necessary as a matter of international law to reassess whether an armed attack is imminent prior to every subsequent action taken against that group, provided that hostilities have not ended." The nature of the threat Israel is addressing renders the scope of this campaign proportional as an act of self-defense. It is difficult to imagine a self-defense objective more vital than eliminating the threat of being attacked with a nuclear weapon by a state that has already launched hundreds of ballistic missiles and drones into your territory and repeatedly threatened to destroy you. If assessed through the lens of self-defense, a military campaign focused on preventing Iran from achieving its objective of annihilating Israel is clearly proportional. Lt.-Col. Geoffrey Corn (ret.), a Texas Tech University law professor, previously served as the U.S. Army's senior law of war expert. Orde Kittrie, an Arizona State University law professor, previously served as the lead U.S. State Department attorney for nuclear issues.