The president now asserts the right, but he does not actually have it. If our ossified judicial system has any remaining merit, he will (eventually) be called to account for his unlawful use of military force--assuming his successor doesn't pull a Ford and pardon him.
How about the unlawful use of torture by the prior regime? This stuff goes back a ways, are you going to put every living former commander in chief on trial?
EDIT: Good point.