It seems to me that there’s a more common example of the separation of powers question being discussed in this thread (and I’m not trying to hijack the topic; I think this is a relevant analogy). Namely, what about when a Senator runs for president and wins, as Obama did? Is he required to give up his Senate seat, or could he theoretically serve in both positions simultaneously (setting aside the insane level of personal organization that such an endeavor would require)?
Something similar happened in Minnesota in the 1970s when the governor resigned with the understanding that his successor would appoint him as senator (to replace Mondale who had become VP). This was Wendell Anderson (of “the Minnesota Miracle” Time magazine cover)
The easiest route is for Obama to resign and have Biden make the appointment…
As mentioned previously, there is a specific prohibition in the Constitution against members of Congress simultaneously holding other federal office. A member of Congress who is elected or appointed to another federal office must resign in order to serve.
There is no such specific prohibition in the Constitution between the Executive and Judicial branches.
You are right- executive branch employees are not constitutionally prohibited from being judicial branch employees at the same time, and there is a shocking precedent which I only learned of a few minutes ago per Wiki:
John Marshall served as both Secretary of State and Chief Justice of the Supreme Court!
Even though he held both offices for only 32 days it seems to me that absent intervening legislation nothing could prevent a US President from serving as Chief Justice simultaneously. Worse such an event would seem to logically command support from the orininalist-textualist school of legal philosophy, which is sure remain influential even with the departure of Antonin Scalia.
Is there anyone besides me who would not put it past a President Donald Trump to nominate himself for Chief Justice?
It is not unprecedented. See reply #24 to this thread.
I hope so!
Excuse me, but Trump would of course have to wait for an opening in the court, and the next opening is unlilkely to be that of Chief, since Roberts is young and healthy. However, several of the liberal justices are not young and healthy, and a miscreant conservative president might have an opportunity such as I depict in the near future. Naturally both sides can play that game, but the first to strike would have an advantage in a lifetime appointment situation.
I can’t really imagine a situation where it would get very far at all. A SC nominee has to be confirmed by the Senate, and I can’t see any senators even entertaining the notion of a president nominating themselves. They would all vote no if and when they were required to actually vote…
Obama just has to express an interest and make a few Taft references, and he probably has a decent shot of getting a nomination before he’s too old to do anything with it.
Although the president specifically is prohibited from receiving any “Emolument from the United States” except for his salary as president, but the justices of the Supreme Court must “receive for their Services a Compensation.” I don’t know how those could be reconciled.
The President resigns just before taking the oath. This is not a problem.
I believe there is a prohibition on someone simultaneously working for more than one branch of the government (Executive, Legislative, and Judicial). If that’s true, one would have to resign the Presidency (Executive branch job) before accepting a job with the Judicial branch.
I believe that would be the only legal problem, leaving only practical problems like getting Congress to confirm it.
I suppose Taft could use some company, if somebody wants to try.
(Taft is the only person to have been both President and a Justice of the Supreme Court, He is also the heaviest person to have been either,)
House of cards season 5 plot? 
Yes, someone can be the president, then be a Supreme Court justice. But people are saying someone can be the president and a Supreme Court justice simultaneously, which I don’t think is true because of the salary issue.
I theory you can refuse your salary as president, Trump says he is going to if he’s elected. Now thats a sobering thought God-Emporer Trump assigning himself as Chief Justice of the Supreme Court…
That doesn’t solve the problem. The president isn’t allowed to accept any money from the United States except his or her compensation for being president. Turning down the presidential salary doesn’t somehow allow the judicial salary. I guess it could be argued that refusing to cash the check means no emolument was “received” but that seems pretty thin.
That entirely depends on a court decision in the highly unlikely case someone was to actually try this. Plenty of things that are “pretty thin” have been accepted as legal.
So he can turn down the judicial salary. As a practical matter, the Senate would vote down the nomination as a conflict of interest if for no other reason, but there is no real constitutional prohibition.
Check out Marbury v. Madison. Famous for being the very first case of SCOTUS declaring an act of congress unconsitutional and the ruling was, in effect, that having a judge issue a writ of mandamus (“you must”) on the president violated the separation of powers. There is nothing in the constitution that explicitly authorizes the court to declare a law unconstitutional, although you could (and many have) argue that it is implicit in the supremacy clause. Roughly, laws passed in accordance with this constitution…are the supreme law of the land. And laws not in accordance? Who decides? In the early days, some argued that this was the province of the president and he could veto such a law. But if he was overridden? Lots of unanswered questions.
Nitpick: the ruling was that SCOTUS did not have the authority to issue the writ because the Judiciary Act unconstitutionally expanded its jurisdiction; the implication was that Marbury could have had a writ had he filed his action in a lower federal court.
The OP is actually asking if a President can nominate himself. As I stated above this would be an unprecedented example of acting in one’s own political self-interest, and even if it couldn’t be proven to be unconstitutional it would be career suicide. Both for the President nominating themselves and for any senators who seriously entertained the idea of going along with it. Even if an outgoing President did it as the last official act of his administration it would be perceived as wildly inappropriate (the self-nomination, not the idea of a former president serving on the court).