A federal appeals court appeared skeptical of President Donald Trump’s sweeping tariff policy on Thursday, grilling the Justice Department on whether the president had lawfully implemented the key part of his trade policy.

In a courtroom steps away from the White House in downtown Washington, D.C., the 11-judge panel of the U.S. Court of Appeals for the Federal Circuit heard arguments in a legal challenge to the bulk of Trump’s tariffs in a case that appears destined for the Supreme Court.