The last time U.S. District Judge Aileen Cannon ruled on a case involving Donald Trump and his alleged hoarding of classified documents, the dressing-down from appellate judges above her was stern and blunt. Last year, Cannon, a Trump appointee, approved Trump’s demand for an outside arbiter to examine documents that federal agents had seized from the former president’s Mar-a-Lago residence in Palm Beach, Florida. Trump’s bid clearly was a stall tactic aimed at slowing the Justice Department’s investigation, and Cannon facilitated it. The Justice Department appealed to the U.S. Court of Appeal...