Jimmy Carter was apparently quite the diplomat in the years after his presidency -- he has gone on secret missions for every U.S. president after him except Ronald Reagan -- but not much of a secret keeper.

According to Michael Duffy, Time editor and author of "The President's Club: Inside the World's Most Exclusive Fraternity," Carter traveled to some of the world's most dangerous places, producing "hair-raising" stories. But when President Obama decided to send Carter to North Korea, the administration made him sign a 10-point legal document issuing what he could and could not do in an effort to reel in the free-speaking Carter.

"Number 10 was you will never, ever speak to the press about it," Duffy told a crowd at the Woman's National Democratic Club last week. "Which was funny when Carter explained it to me. ..."