The President is Commander-in-Chief of the military, so the military cannot arrest him. That would constitute a mutiny.
Only resignation, death, conviction by the Senate in an impeachment proceeding, or a 25th Amendment removal can remove the President.
If there is a military coup and the Constitution is abrogated, then all the rules and constitutional procedures go out the window.
:: The President is Commander-in-Chief of the military, so the military cannot arrest him. ::
Where’s the football?