In my random research to determine whether anyone has ever said that a Supreme Court justice holds an “office under the United States,” and is thus subject to the incompatibility clause, I came across this question from Story’s commentaries that I don’t think I have ever considered.
Article II provides an alternate route for the appointment of “inferior Officers”:
but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments
In Section 1593 of the Commentaries, Story queries if the judges of the inferior courts are inferior officers:
Whether the Judges of the inferior. courts of the United Slates are such inferior officers, as the constitution contemplates to be within the power of congress, to prescribe the mode of appointment of so as to vest it in the president alone, or in the courts of law, or in the heads of departments, is a point, upon which no solemn judgment has ever been had. The practical construction has uniformly been, that they are not such inferior officers. And no act of congress prescribes the mode of their appointment. See the American Jurist for October, 1830, vol. 4, art. V.p. 298.
I found that edition of American Jurist on Google books–and guess what! It’s a citation to a letter that Chief Justice John Jay and the Associate Justices wrote to President George Washington! Washington had penned a letter to the Court on 4/3/1790.
The note suggests that the power to appoint Article III judges cannot be vested by Congress.
That would be really anomalous if the courts of law could receive the power from congress to appoint other judges.