There's an interesting legal loophole that @profbriankalt discovered back in 2005, where he identified a small portion of Yellowstone Park that, by a literal reading of the 6th amendment, one could legally commit murder and no prosecutor could legally bring charges.

In practice, people tend not to worry about this oddity, since there's a presumption that the system will figure out a way to "do the right thing" for a crime; and, in fact, a federal judge did manage to get a plea out of a poacher who tried raising this loophole as a defense.

There's an interesting and closely related thing going on right now. In Nixon v. Fitzgerald, the Supreme Court established that a sitting president has Absolute Immunity to civil prosecution from the moment they take office until the moment they step down.

Meanwhile, we're seeing arguments raised, right now, that a President cannot be impeached after they leave office, even for actions taken while in office. Like the Yellowstone "Zone of Death," accepting this argument in the face of Nixon v. Fitzgerald creates a loophole.

This line of argumentation would establish a window near the end of every president's term where the civil court system would lack authority, per Fitzgerald; and Congress would ALSO lack authority, since the impeachment and conviction process cannot take place instantaneously.

As with Yellowstone, it's clear that no one, from the founding fathers to the modern judiciary, intended that the Constitution include windows of lawlessness (either geographic or temporal), so common sense demands that either Fitzgerald must go, or calls to dismiss are wrong.

The Fitzgerald opinion explicitly cited impeachment as a check on Presidential malfeasance as justification for immunity. If we remove this recourse, then the rationale for immunity falls apart.

P.S. Details on the Yellowstone "Zone of Death" here: https://en.wikipedia.org/wiki/Zone_of_Death_(Yellowstone)

And clicking through to Brian Kalt's profile, I see that he has addressed this issue (albeit from a different angle) in a very evenhanded and nonpartisan way, back in 2001: https://digitalcommons.law.msu.edu/facpubs/21/