Rodney

You're covering two different issues here: unauthorized biographies and trademarks.

The estate of Edgar Rice Burroughs has trademarked anything to do with the name "Tarzan" and fights furiously against any unauthorized use of the name. Because if they allow common use of the name without permission, they lose control of it. I suspect that you'd have a hard time if you used the word "Tarzan" in a book title without their permission.

Unauthorized biographies draw on public sources, news articles, and third parties who know about the biographical subject and are willing to talk about him/her. Since the subject of the biography is not involved, no permission is required. And as a public figure, the person's right to privacy is limited.

Without this way of operating, journalism as we know it couldn't exist. Journalists often write stories about people who really don't want their name in the paper -- criminals, crooked politicians, etc -- and they gather facts about the person usually without his or her permission. An unauthorized biography is basically a piece of journalism, and is unassailable as long as it hews to journalistic rules: all firm assertions attributed to named sources, no "reckless disregard for the truth" and so on.

The only guy I remember who got into serious trouble from writing an authorized biography was a guy named Clifford Irving back in the '70s. He wrote an unauthorized bio of tycoon Howard Hughes back in the '70s and, it turns out, made a lot of stuff up. Hughes even came out of seclusion to refute the book.