I agree, not in the constitution anyway... If anything it would have to be an obscure senate rule or some precedent set somewhere if it were mentioned anywhere.
Seems like it would be a good basis for a rule to prevent impeachment based on lies that are knowingly told as lies and only used for political persecution and/or advantage...
This has been an attack on every one of US who voted for him and has limited Trump’s ability to govern effectively for 3/4 of his first term based purely on lies!
Just imagine how much he could have done by now if not for the treasonous, seditious, obstructionist demoCraps!