On April 7, the world breathed a collective sigh of relief as U.S. President Donald Trump announced a two-week cease-fire with Iran. Oil prices retreated and markets rallied rapidly on the news. But before the cease-fire was agreed, Trump engaged in an astounding rhetorical campaign in which, among other shocking things, he threatened to destroy Iran’s power plants and bridges.

A quick and only partial review: On March 21, Trump posted on his social media site that the United States would “obliterate their [Iran’s] various POWER PLANTS, STARTING WITH THE BIGGEST ONE FIRST” if Iran did not reopen the Strait of Hormuz within 48 hours. On March 30, he then threatened that if the Strait of Hormuz remained closed, the United States would be “blowing up and completely obliterating all of their Electric Generating Plants, Oil Wells and Kharg Island (and possibly all desalinization plants!).”

On April 7, the world breathed a collective sigh of relief as U.S. President Donald Trump announced a two-week cease-fire with Iran. Oil prices retreated and markets rallied rapidly on the news. But before the cease-fire was agreed, Trump engaged in an astounding rhetorical campaign in which, among other shocking things, he threatened to destroy Iran’s power plants and bridges.

A quick and only partial review: On March 21, Trump posted on his social media site that the United States would “obliterate their [Iran’s] various POWER PLANTS, STARTING WITH THE BIGGEST ONE FIRST” if Iran did not reopen the Strait of Hormuz within 48 hours. On March 30, he then threatened that if the Strait of Hormuz remained closed, the United States would be “blowing up and completely obliterating all of their Electric Generating Plants, Oil Wells and Kharg Island (and possibly all desalinization plants!).”

On April 2, he pledged that “Our Military . . . hasn’t even started destroying what’s left in Iran. Bridges next, then Electric Power Plants!” The same day, he crowed that “biggest bridge in Iran comes tumbling down, never to be used again — Much more to follow! IT IS TIME FOR IRAN TO MAKE A DEAL BEFORE IT IS TOO LATE, AND THERE IS NOTHING LEFT OF WHAT STILL COULD BECOME A GREAT COUNTRY!” Then, on April 4, he warned that “Time is running out – 48 hours before all Hell will reign down on them,” again referring to Iran.

These statements were widely—and rightly—condemned as threats to perpetrate war crimes. Yet Trump has not renounced them. What’s more, the U.S. Defense Department evidently developed a package of targets to attack, apparently to fulfill Trump’s directives. And some commentators have even argued that they were successful in achieving a cease-fire.

As a result, it remains important to understand the legal framework that prohibits the threatened attacks and the consequences of carrying them out for the United States and its service members.

The conduct of warfare is regulated by a special body of law known as “international humanitarian law” (IHL) or the........

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