They’ve also made much of the fact that the presidential authority to pardon is constitutionally unreviewable, so even if the president orders someone to commit a crime, he can pardon them preemptively. His appointment power is similarly in the constitution, so he can also fire and replace them until he finds someone willing to do it.
Are we really left with ‘if the president were to issue illegal orders to his staff, Congress would definitely impeach him’?