The US government has explained why it regards its military strikes against Iran as lawful. It says its actions amount to self-defence — both in protecting itself and in collective self-defence of Israel.
In a detailed statement released on Tuesday, Reed Rubinstein, legal adviser to the US state department, responded to critics who had claimed that US military operations were inconsistent with the United Nations charter.
He wrote:
In truth, the United States is acting well within the recognised contours of international law relating to the use of force and self-defence. This legal assessment is grounded in facts demonstrating Iran’s malign aggression over decades, particularly in Iran’s escalatory attacks against the United States, Israel and others in the region for years, which precipitated an international armed conflict that predated US combat operations on February 28 and that continues to this day.
“The operations recommenced in late February were part of an armed conflict with Iran that has been ongoing for years and, at the very least, since June 2025,” Rubinstein wrote. “Under well-established rules of international law, it is reasonable to conclude that this conflict did not end in the interim.”
The legal adviser’s statement deals mainly with the jus ad bellum, the legal justification for US and Israeli strikes on Iran. It is consistent with Israel’s own position, set out shortly after the current round of hostilities began.
“As a matter of international law,” Rubinstein said, “there is no requirement to continually reassess the jus ad bellum principles of necessity and proportionality in the context of an ongoing armed conflict.”
Even if there had been, he added, “those customary international law principles are satisfied here because of the scale and continued nature of the threat posed to the security of the United States and Israel”.
Rubinstein concluded:
The United States has acted well within its international law obligations with respect to its use of force since operations began in late February. Iran, by contrast, has acted as any reasonable observer would have expected — lashing out against its neighbours, targeting Israeli civilians, murdering its own people, unlawfully closing the Strait of Hormuz and wreaking havoc throughout the region.
The regime’s outrageous, albeit predictable, behaviour only further underscores the fundamental necessity, utility, reasonableness, and lawfulness of Operation Epic Fury’s mission and goals.
The legal adviser’s statement came a couple of days after Mike Waltz, the US ambassador to the UN, had outlined his government’s legal position in interviews with the US news networks NBC, ABC and CBS. He was talking there about jus in bello, the law governing the conduct of hostilities, and whether it would now be lawful for the US to bomb bridges and power plans in Iran.
In a response to Waltz’s comments yesterday, three legal academics set out the limits, as they saw them, to what the law of armed conflict would permit.