I assume it's the Maine courts at this point.
Yes it was. FPOTUS#45 was given due process as part of a civil bench trial in Colorado.
"PROVEN GUILTY" is a standard applied to criminal cases. "ENGAGED IN" is the Constitutional standard cited in the 14th Amendment.
The President and Vice President being elected does not make them not officers. Just as Senators and Representatives, also elected, are still subject to the 14th.
Read the 14th, insurrection against the Constitution, not the President.
Also, if you go back to the Congressional record and read about the debates there was a specific question as to whether the "any officer" provision applied to the Office of the President and the answer was yes.
WW