In a highly unusual legal move, lawyers for the Justice Department said in court papers that Mr. Trump was acting in his official capacity as president when he denied ever knowing Ms. Carroll and thus could be defended by government lawyers — in effect underwritten by taxpayer money.
Though the law gives employees of the federal government immunity from most defamation lawsuits, legal experts said it has rarely, if ever, been used before to protect a president, especially for actions taken before he entered office.