Ordering Navy's Seal Team 6 to assassinate a political rival is not an official act of the President because the purpose is not within Presidential powers.

Albaby has essentially stated the same, but I still don't see the reason. Isn't one of the president's constitutional powers - and in fact a mandatory duty - to protect the U.S. from threats both foreign and domestic? If so, why can't Biden (or any other POTUS) simply claim that as the reason for assassinating (or jailing) anyone, including a former - and potentially future - threat to America?

Let me try and clarify. Hypo: The US has information that a suitcase sized large nuclear bomb is being carried by X to Chicago. Pres gives OK, and the person is killed while taking the suitcase, but the suitcase turns out to be a phony mock up. Does that fall within Presidential powers? I think so, and even if not so, I doubt it would be charged, but if it was, acquittal is in order.

Hypo #2: The Pres gives the order to take into custody in any manner a political opponent, with the reason being National Security. So secure even the reason(s) can't be disclose. We establish that the order goes up to a high officer who talked to the President just before giving the order. The opponent ends up comatose in the hospital. We can summons the officer to the President. The President will, using the cover that he's a national security advisor, claim immunity. This will most likely be decided by the DOJ, or by the courts, winding its way up. So it will take time, but if there is a statute it is most likely tolled by the decision making process. Politics can intervene and slow the process, and may kill it. Who knows? Elect Trump and we'll find out for sure. :)