Bring it to the Supreme Court. At its heart are many vital Constitutional questions that need to be answered.
It doesn’t matter who appointed the judges.
What matters is whether we have, or do not have, a unitary executive as described in Article II.
This has been a festering sore since Watergate (and maybe since 11/22/63), and it needs to be resolved.
The President is not a King, in that he cannot make laws or give orders to Congress. But if he is not in charge of the Executive Branch, then the crown is truly hollow.