Text 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.[4]
Holding the G7 conference at his own resort would involve accepting money from heads of foreign states, which would be a direct violation of the emoluments clause.
Him having businesses in other countries and accepting said money at those locations would also be a direct violation of the emoluments clause.
Take it up with Senator Bob Corker and Judge Andrew Napolitano. Not to mention we are talking about t-shirts here. Do you even know how business and corporations work? ---