Show me in the laws written covering a special prosecutor/investigator that says the president can do this. Until you can point to that this point is not in dispute.
Show me otherwise. Prove your point... that is right, you cannot.
The "Special Prosecutor" is appointed and serves by discretion of the DOJ. An executive department serving at the discretion of the President.
Really, it is not in dispute. The Pres can fire the DOJ head if the DOJ head does not do what he wishes. Including firing a special prosecutor. Hell, the Executive..The Pres can do it himself if he wishes.
Now that may well trigger an impeachment. But the President has sole power over the Executive branch.
Care to prove otherwise?