Donald Trump became famous for being a blowhard New York billionaire, and now has just become a middling reality TV show actor with outlandish hair. Trump has never been a really rich fellow, as a lot of his funding is based on debt and loans, which is effectively smoke and mirrors. His hair will probably be famous longer than he himself will be.
Love Donald Trump or hate him - you certainly can identify him immediately in a photo. This is largely because of his unique hair. I don't think you could find many people suggesting that he has
'good hair' - but its definitely 'legendary' in the sense that its so highly recognizable.
Unfortunately for Donald Trump most people remember him for his hair. It has turned into nothing short of pop culture as many have made fun of it over the years. His hair is by far lengendary and will more than likely remain that way as it doesn't seem he's made any attempt to change it.
A gray area needs to exist in the law where strict copyright does not apply simply because it would be socially unenforcable. For example, this is why retailers such as Urban Outfitters are able to "get away" with copying independent designers' work, as copyrights do not apply to fashion. In the same way, trademarking a hairstyle should not be permissible.