“When the SCOTUS finds that a law passed by Congress is Unconstitutional, the effect is that it never was a law, and all actions taken under that law are null and void—retroactively. The same principle would apply to any supposedly official acts of Obama—they would be null and void, retroactively, as though they had never occurred. “
Bills he signed into law should go through a new vote by Congress and be signed or not by a new president. Executive orders an illegitimate president made on his own would by logic become null and void. Supreme Court justices seems to pose a stickier issue, because the Congress confirmed the suggested person after the president nominated them.
The Constitution grants no power to the Congress to approve a nominee not nominated by a President.