Okay. Further investigation.
The current regulations covering the Special Counsel are under 28 CFR Part 600.
600.7(d) reads:
The Special Counsel may be disciplined or removed from office only by the personal action of the Attorney General. The Attorney General may remove a Special Counsel for misconduct, dereliction of duty, incapacity, conflict of interest, or for other good cause, including violation of Departmental policies. The Attorney General shall inform the Special Counsel in writing of the specific reason for his or her removal.
I’m calling this one … same horse, different jockey.
The above sets forth the applicable law that Trump would need to break in order to have Smith removed.
Second source:
Aside from review of particular actions, the regulations also grant the Attorney General authority to discipline or remove the special counsel. This authority may be exercised “only by the personal action of the Attorney General.” In other words, to comply with the regulations, the Attorney General himself must remove the special counsel, not the President or a surrogate (unless, as noted previously in this report, the Attorney General has recused himself in the matter under investigation). A decision to remove the special counsel must be made with “good cause,” such as misconduct, a dereliction of duty, incapacity, the existence of conflicts of interest, or violation of departmental policies. The Attorney General must report his decision to remove the special counsel, with an explanation of that decision, to both the Chairman and Ranking Members of the Judiciary Committees of Congress.