The Supreme Court just confirmed what was already practiced.
It has always been "do it and find out." As you pointed out, Obama killed Americans overseas, and nobody prosecuted him for it. The remedy under the Constitution for a President who abuses his power isn't "prosecute him years later." It is for Congress to remove him. If he orders the assassination of an American by Seal Team 6, and Congress doesn't act, then I guess it was legal.
Nobody has been prosecuting ex-Presidents. That's why we don't know what all they can be prosecuted for. Which the Supreme Court didn't decide. Because arguably this made-up act is un-Constitutional -- outside the legitimate authority of the President -- and therefore could not possibly qualify as official acts.
It has always been "do it and find out." As you pointed out, Obama killed Americans overseas, and nobody prosecuted him for it. The remedy under the Constitution for a President who abuses his power isn't "prosecute him years later." It is for Congress to remove him. If he orders the assassination of an American by Seal Team 6, and Congress doesn't act, then I guess it was legal.
Nobody has been prosecuting ex-Presidents. That's why we don't know what all they can be prosecuted for. Which the Supreme Court didn't decide. Because arguably this made-up act is un-Constitutional -- outside the legitimate authority of the President -- and therefore could not possibly qualify as official acts.