I was reading the October 2000 memorandum to the Attorney General regarding A Sitting President's Amenability to Indictment and Criminal Prosecution, which you can also read here:
https://www.hsdl.org/?view&did=742477
From the memorandum:
So, while a "law enforcement officer" enjoys their position, it is " inconsistent with the constitutional structure" to be able to prosecute a case against them.
https://www.hsdl.org/?view&did=742477
From the memorandum:
in light of the President's unique powers to supervise executive
branch prosecutions and assert executive privilege, the constitutional balance generally should favor the conclusion that
a sitting President may not be subjected to indictment or criminal prosecution. According to this argument,
the possession of these powers by the President renders the criminal prosecution of a sitting President inconsistent with
the constitutional structure. It was suggested that such powers, which relate so directly to the President's status as a law
enforcement officer, are simply incompatible with the notion that the President could be made a defendant in a
criminal case. The memorandum did not reach a definitive conclusion on the weight to be accorded the President's
capacity to exercise such powers in calculating the constitutional balance, although it did suggest that the President's
possession of such powers pointed somewhat against the conclusion that the chief executive could be subject to
indictment or criminal prosecution during his tenure in office.
So, while a "law enforcement officer" enjoys their position, it is " inconsistent with the constitutional structure" to be able to prosecute a case against them.