The Move to 'Restore' the 13th Amendment - Newsweek
The Republican party of Iowa's platform calls for "the reintroduction and ratification of the original 13th Amendment, not the 13th amendment in today’s Constitution.", which forbids any person who accepts a "title of nobility" from a foreign country from ever holding political office.
There are, of course, other implications of Thirteenthism, such as ensuring that the United States never again suffers the humiliation of having a president win the Nobel Peace Prize. That was just what the Iowa Republicans had in mind, according to Plogmann [GOP Communications Director], who wrote in an e-mail that the plank “was meant to make a statement about the delegates’ opinion about Mr. Obama receiving the prize.” (Presumably they didn’t mind if, in the process, they were also making a statement about any American scientist or writer unlucky enough to win a Nobel.) Unfortunately for them, the Department of Justice looked into whether Obama needed Congressional approval to accept the Nobel under the existing emoluments clause, and based on the meaning of “foreign state” (which would not cover the Nobel Prize Committee) concluded that he did not.