You are conveniently ignoring the Constitutional mechanisms for removing a President. No one on this planet, including you, can now declare him not to be President. Who would that be? The Supreme Court, the Congress, the Park Police, Simon? It can’t be done as a matter of law. The Senate, however, could act on an article of Impeachment delivered by the House stating that the President was ineligible for office and therefore should be removed. The Senate could hold a trial and remove him. I just don’t know of any other mechanism, including one that I have heard that suggested that it be done by the Joint Chiefs of Staff. That’s called a military Coup d’Etat and I don’t think that will happen.
What is the mechanism for removing usurpers, if not through impeachment?
No I'm not. The Constitution clearly states: "The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors." It says nothing about usurpers.
You are ignoring the requirement that in order to be President, one must be a natural born citizen, over 35 and a resident of the US for 14 years.
Since the courts have been delegated the power to try "all Cases, in Law and Equity, arising under this Constitution, the Laws of the United States, and Treaties made, or which shall be made, under their Authority", it would seem to fall to them to determine if someone meets the requirements, or the meaning of the Natural Born Citizen" term. So far they have declined to do so, despite the many attempts to get them to do their job.
Arrest and drag away for trial on criminal charges the bunk artist conman. How would you do it, poseur?