Michael McConnell, a former appeals court judge appointed by President George W. Bush, has compared the tariffs case with a 1952 ruling, Youngstown Sheet & Tube Company. In that case, the Supreme Court ruled that President Harry Truman couldn’t take control of steel mills to supply armaments for the Korean War. It laid down the principle, Mr. McConnell wrote in a New York Times op-ed, that “even in an emergency, the president cannot take upon himself powers that are granted neither by the Constitution nor by congressional statute.”

If the Trump tariffs are upheld, it would, by contrast, “be a major step toward a presidency that does whatever the president wishes to do,” wrote Professor McConnell, who directs the Constitutional Law Center at Stanford University.