President Trump’s promised appearance on Tuesday at the United States Court of Appeals at Washington underscores the stakes of a decision that could — though it’s a long shot — end Special Counsel Jack Smith’s case before it goes to trial. 

A panel of three appellate circuit riders is set to hear oral arguments as to whether presidential immunity is broad enough to shield Mr. Trump from prosecution on charges that he criminally conspired to overturn the results of the 2020 presidential election. A district court judge, Tanya Chutkan, has ruled that Mr. Trump cannot avail himself of immunity. 

If the appeals court overrules Judge Chutkan and agrees with Mr. Trump that he is entitled to “absolute” immunity by virtue of the office he once held, Mr. Smith’s argument that the 45th president operated outside the ambit of his office will fail. Whichever side loses will have the right to ask for an en banc hearing of the D.C. Circuit and to petition the Supreme Court to take the case.

In Georgia on Monday, Mr. Trump also filed a brief staking his claim to immunity in another criminal case, brought against him by the district attorney of Fulton County, Fani Willis. His team writes that the “unbroken historic tradition of presidential immunity is rooted in the separation of powers and the text of the Constitution” and that he has been charged for “acts that lie at the heart of his official responsibilities as President.”

In Georgia and at the District of Columbia, Mr. Trump’s position is that “absolute immunity shields him from criminal prosecution as well as civil suit.” The exclusive method, he writes, to “proceed against a President for crimes allegedly committed in office is by impeachment in the House of Representatives and trial in the Senate.” Mr. Trump was impeached for incitement to insurrection, but he was discovered by the Senate to be not guilty and acquitted. 

While courts have never had occasion to consider the reach of a former president’s criminal immunity — or a sitting president’s, for that matter — they have opined on immunity in a civil context. In Nixon v. Fitzgerald, from 1982, the Supreme Court held that the president’s “absolute immunity extends to all acts within the ‘outer perimeter’ of his duties of office.”

The Nine explain that a “rule of absolute immunity for the President does not leave the Nation without sufficient protection against his misconduct” because the “President is subjected to constant scrutiny by the press” and “vigilant oversight by Congress also may serve to deter Presidential abuses of office.”

Judge Chutkan, though, ruled that immunity “does not confer a lifelong ‘get-out-of-jail-free’ pass” because “America’s founding generation envisioned a Chief Executive wholly different from the unaccountable, almost omnipotent rulers of other nations at that time.” She finds “no evidence that any of the Constitution’s drafters or ratifiers intended or understood” former presidents to be immune from prosecution. 

Mr. Trump, on the other hand, reads American history in a different light, writing in Georgia — in words that will likely be echoed in the circuit courtroom at Washington, D.C., Tuesday — that “historical practice over 234 years confirms that the power to indict a current or former President for official acts does not exist.” 

The 45th president took to Truth Social on Monday to declare that he would be “attending the Federal Appeals Court Arguments on Presidential Immunity in Washington, D.C., on Tuesday. Of course I was entitled, as President of the United States and Commander in Chief, to Immunity.” It is not clear if Mr. Smith will be in attendance as well.