The former president says his acquittal by the Senate in his second impeachment trial, for inciting insurrection, bars any prosecution on similar grounds.There is almost nothing in the words of the Constitution that even begins to support former President Donald J. Trump’s boldest defense against charges that he plotted to overturn the 2020 election: that he is absolutely immune from prosecution for actions he took while in office.A federal appeals court will hear arguments on the question next week, and the panel will consider factors including history, precedent and the separation of powers. But, as the Supreme Court has acknowledged, the Constitution itself does not explicitly address the existence or scope of presidential immunity.In his appellate brief, Mr. Trump said there was one constitutional provision that figured in the analysis, though his argument is a legal long shot. The provision, the impeachment judgment clause, says that officials impeached by the House and convicted by the Senate are still subject to criminal prosecution.The provision says: “Judgment in cases of impeachment shall not extend further than to removal from office, and disqualification to hold and enjoy any office of honor, trust or profit under the United States: But the party convicted shall nevertheless be liable and subject to indictment, trial, judgment and punishment, according to law.”All the clause says in so many words, then, is that “the party convicted” in the Senate can still face criminal prosecution. But Mr. Trump said the clause implied something more.The clause “presupposes that a president who is not convicted may not be subject to criminal prosecution,” Mr. Trump’s brief said.A friend-of the-court brief from former government officials said Mr. Trump’s position had “sweeping and absurd consequences,” noting that a great many officials are subject to impeachment.“Under defendant’s interpretation,” the brief said, “the executive would lack power to prosecute all current and former civil officers for acts taken in office unless Congress first impeached and convicted them. That would permit countless officials to evade criminal liability.”Mr. Trump also made a slightly narrower but still audacious argument: “A president who is acquitted by the Senate cannot be prosecuted for the acquitted conduct.”Mr. Trump was, of course, acquitted at his second impeachment trial, on charges that he incited insurrection, when 57 senators voted against him, 10 shy of the two-thirds majority needed to convict.The idea that the impeachment acquittal conferred immunity from prosecution may come as a surprise to some of those who did the acquitting.Take Senator Mitch McConnell, the Republican leader, who voted for acquittal. Shortly afterward, in a fiery speech on the Senate floor, he said the legal system could still hold Mr. Trump to account.“We have a criminal justice system in this country,” Mr. McConnell said. “We have civil litigation. And former presidents are not immune from being held accountable by either one.”That suggests that Mr. Trump’s reading of the clause is far from obvious, but the Justice Department has said that it is not wholly implausible. In 2000, its Office of Legal Counsel issued a 46-page memorandum devoted to just this question. It was called “Whether a Former President May Be Indicted and Tried for the Same Offenses for Which He was Impeached by the House and Acquitted by the Senate.”The argument that such prosecutions run afoul of the Constitution “has some force,” according to the memo, which was prepared by Randolph D. Moss, now a federal judge. But, it went on, “despite its initial plausibility, we find this interpretation of the impeachment judgment clause ultimately unconvincing.”It added: “We are unaware of any evidence suggesting that the framers and ratifiers of the Constitution chose the phrase ‘the party convicted’ with a negative implication in mind.”More fundamentally, the memo said, “impeachment and criminal prosecution serve entirely distinct goals.” Impeachment trials involve political judgments. Criminal trials involve legal ones.In a brief filed on Saturday, Jack Smith, the special counsel, wrote that “acquittal in a Senate impeachment trial may reflect a technical or procedural determination rather than a factual conclusion.” The brief noted that at least 31 of the 43 senators who voted to acquit Mr. Trump at the impeachment trial said they did so at least in part because he was no longer in office and thus not subject to the Senate’s jurisdiction.Mr. Trump’s reading of the provision “would produce implausibly perverse results,” Judge Tanya S. Chutkan, who is overseeing his trial in Federal District Court in Washington, wrote in a decision last month rejecting Mr. Trump’s claim of absolute immunity.She noted that the Constitution permits impeachment for a narrow array of offenses — “treason, bribery or other high crimes or misdemeanors.”Under Mr. Trump’s reading, Judge Chutkan wrote, “if a president commits a crime that does not fall within that limited category, and so could not be impeached and convicted, the president could never be prosecuted for that crime.”“Alternatively,” she went on, “if Congress does not have the opportunity to impeach or convict a sitting president — perhaps because the crime occurred near the end of their term, or is covered up until after the president has left office — the former president similarly could not be prosecuted.”She added that President Gerald R. Ford’s pardon of former President Richard M. Nixon, who resigned as calls to impeach him for his role in the Watergate scandal grew, would have been unnecessary under Mr. Trump’s reading. More