In terms of fiduciary and Constitutional - or Constitutional (including fiduciary) - obligations,
is there any penalty for violating an Oath of Office?
> Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:– I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.
Impeachment, removal from office, being barred from ever holding office again. Those are separate but need to happen in order.
That’s the limit of it, by design I think. The lack of criminality or even civil offense means the job is predicated on trust to achieve political goals. Once trust is lost, the individual must be removed from office or immense damage will ensue.
I've never heard of double jeopardy for impeachment; being impeached does not preclude criminal prosection for the same offense.
FBI's assessment of presidential immunity might should be reviewed in light of the court's recent ruling on same and the fact that they are an executive branch department of government. They work for the executive - as evidenced by the firing of James Comey - so we can't trust their assessment of his immunity.
US Constitution > Article II.S1.C8.1 "Oath of Office for the Presidency": https://constitution.congress.gov/browse/essay/artII-S1-C8-1... :
> Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:– I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.
US Constitution > Article II.S1.C8.1.5 "Violation of the Presidential Oath" https://constitution.congress.gov/browse/essay/artII-S1-C8-1...
Oath of office of the president of the United States: https://en.wikipedia.org/wiki/Oath_of_office_of_the_presiden...