FYI ping.
No title of nobility shall be granted by the United States: and no person holding any office of profit or trust under them, shall, without the consent of the Congress, accept of any present, emolument, office, or title, of any kind whatever, from any king, prince, or foreign state.
We can debate if this applies but when I first heard about it, this was the first thing that popped in my head.
Obama would have to resign as POTUS to accept the Chairmanship of the UN Security Council.
Do it O.