Can the president appoint him- or herself to the Supreme Court?
Are there any provisions in the United States Constitution, or other U.S. laws or regulations, that specifically prohibit—or otherwise preclude—the president from appointing him- or herself to the Supreme Court?
One possible consideration: At a minimum, since this would likely necessitate some overlap where the person has these two jobs at the same time, is it permissible for any single person to receive multiple paychecks from the Federal government on a given payday?
For the purposes of this question, we can assume the Chief Executive is a judge or lawyer and ostensibly qualified to serve as a Supreme Court Justice.
Yes, constitutionally, the POTUS can serve other posts simultaneously.
This is because the Ineligibility Clause of the Constitution only applies to members of the Congress.
No Senator or Representative shall, during the Time for which he was elected, be appointed to any civil Office under the Authority of the United States, which shall have been created, or the Emoluments whereof shall have been increased during such time; and no Person holding any Office under the United States, shall be a Member of either House during his Continuance in Office.
As this article by Quartz mentions that there isn't any law that disqualifies the POTUS from serving other posts simultaneously.
Moreover, there’s nothing in the derivative federal laws that expressly disqualifies the president of the United States from serving simultaneously—either in Title 3 (the president) or Title 28 (the Judiciary)—much less requires his resignation (although if someone does find such a citation, please share).
However, this being said, it doesn't mean that the President (Supreme Court Nominee) will be confirmed by the Senate as all Supreme Court nominees require Senate confirmation:
"he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint ... Judges of the supreme Court..."
However, there likely would be a legal challenge since the executive branch of the government should be independent from the judiciary branch.
Also, a close, but not exact, example to your scenario would be William Taft who served as a Justice on the Supreme Court eight years after his term as POTUS ended. However, Taft did not appoint himself to the post (Warren Harding appointed him).
There may also be a constitutional challange, as this would - in spirit - violate separation of powers.
Putting aside the political difficulties, what could be the merit, basis and/or standing, etc., for the court battles?
@GlennSlayden If the President is confirmed, he would serve like any other justice on the Supreme Court. Also, if the POTUS is a lawyer before, he would be qualified.
Hmm, really, on separation of powers? I'm (obviously) no constitutional lawyer (or lawyer), but SOP seems more like an overarching design fact than an edict. Is there actually imperative language in the Constituion such that "the (three) powers shall and must remain separate?"
Worth mentioning President Taft in this answer, who is very close to meeting the OP's criteria.
@DavidGrinberg Yup, but he served on the Court after he stepped down from the Presidency. Thanks for pointing out!
My comment wasn't referring to that. I stipulated he or she would be qualified for the job. I was wondering what legal approaches could block the appointment. So the question in my comment stands.
@GlennSlayden Though the Constitution doesn't state explicitly that a separation of powers is necessary, but it is considered to be a political doctrine as described in this Wikipedia article
@DavidGrinberg However, Justice Taft did not submit his own name, nor did he appoint himself, which was the nub of the question.
Saying that Taft "stepped down" from the presidency is a bit misleading, as it suggests that he actively chose to leave the presidency. It's the kind of language that I'd expect if he resigned. Taft lost an election and his term ended. More than eight years later, he was appointed to the Supreme Court. Note: I'm not arguing with the technical truth, merely that it reads in an ambiguous way such that it could be incorrect.
(Taft's story is an interesting one -- he didn't *want* to be POTUS in the first place; his personal ambition was to be Chief Justice, but he had family pushing him from behind in a different direction).
@GlennSlayden If you look at the Supreme Court's separation of powers cases, the crux of the doctrine seems to be that branches can't use their otherwise valid powers to do something that properly falls within the purview of another branch or intrudes on its authority. It is certainly at least arguable that the President and Congress together putting the President himself (who pretty much *is* the executive branch) on the Supreme Court is doing exactly this.
@DavidSchwartz Great observation. It's currently not mentioned in the body of any answer on this page, if you want to write it up that way. In fact, your point seems to contradict the boldfaced assertion at the top of this answer.
@DavidSchwartz A president sitting on any federal court would have to recuse himself from, at a minimum, every case in which the United States is a party. It would certainly lighten the workload, but it would also mitigate the separation of powers concerns.
@phoog: All federal judges are required to recuse themselves according to 28 U.S.C. § 455, but unlike other judges, a supreme court judge's decision regarding recusal is not reviewable by anyone besides themselves. Nothing forces them to do so.