As U.S. and Israeli forces pounded Iran, and Tehran and its affiliates retaliated by firing missiles at targets across the Mideast on Monday, the international legal order was caught in the crossfire.

At the heart of the post-World War II global order — United Nations headquarters in New York — Secretary-General António Guterres told the Security Council on Saturday that U.S. and Israeli airstrikes violated international law, including the U.N. Charter. He also condemned Iran's retaliatory attacks for violating the sovereignty and territorial integrity of nations in the Mideast.

Officials in the Trump administration insist that the military campaign is a lawful measure to ensure Tehran does not build nuclear weapons. "It's a matter of global security. And to that end, the United States is taking lawful actions," Trump's U.N. ambassador, Mike Waltz, said.

Iranian Foreign Minister Abbas Araghchi wrote in a letter to the U.N. on Sunday that the killing of Supreme Leader Ayatollah Ali Khamenei "constitutes a grave and unprecedented breach of the most fundamental norms governing relations among States."

On Monday, Defense Secretary Pete Hegseth bullishly defended the U.S. military campaign. "No stupid rules of engagement, no nation building quagmire, no democracy building exercise, no politically correct wars. We fight to win and we don't waste time or lives," he said at the Pentagon.

The war with Iran comes less than two months after U.S. forces swooped into Caracas to capture former Venezuelan President Nicolás Maduro and fly him to New York to face justice.

David Crane, an American expert on international law and founding prosecutor of a United Nations court that prosecuted crimes in Sierra Leone, wrote in an analysis that U.S. attacks in Iran and Venezuela "highlight a dangerous trend: the normalization of unilateral force as a tool of foreign policy. Even when the outcome is positive, the violation of international law and constitutional limits sets a precedent that threatens global stability and undermines America's own legal foundations."

In Washington, many Democrats have called the strikes illegal. They argue that under the Constitution, only Congress has the power to declare war. They say the Trump administration failed to lay out its rationale or plan for the military strikes, and the aftermath.

Congress hurriedly scheduled a war powers debate for Monday over Trump's authority to bomb Iran.