What The Constitution for the United States of America really tells us about emoluments.
From The Constitution for the United States of America, Article 1, Section 9, it states; "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."
From Article 2, Section 1, it states "The President shall, at stated Times, receive for his Services, a Compensation, which shall neither be increased nor diminished during the Period for which he shall have been elected, and he shall not receive within that Period any other Emolument from the United States, or any of them."
Perhaps I missed it, but did Congress authorize a recent President, in 2009, to accept the Nobel Peace Prize from Norway? If Congress did not authorize it, this certainly could have been a violation.
A 1785 common-use dictionary defines "Emolument. Profit; advantage."
According to Article 2, this would not apply to any foreign State or possession of these united States, but only to any of the Domestic States that is a member of these united States of America. With respect to foreign leaders staying in one of Mr. Trump's hotels; the courts properly ruled.
However, dealing also with Article 1 applies to all government officers, within and for these united States of America. With respect to Article 1, any foreign leaders staying in one of Mr. Trump's hotels; the courts incorrectly ruled. When foreign leader stay at a hotel, other people from that country are more likely to try to stay at that hotel, because it lends more credibility, publicity, and more financial receipts/profits. This would be the same as if I owned a Mom & Pop hotel and a famous actor, athlete, etc. stayed there. More people are likely to book reservation and stay, simply because someone famous also did. Thus the advantage gained.