Legal Question in Entertainment Law in New York

There's nothing to prevent you from writing a story based on anyone, celebrity or not. However, the people you write about have rights too and if you violate them, you and your publishers may get sued.

So, unless you are self-publishing (in which case you assume all the risk of legal exposure), if your story's characters are or can be identified as living (and sometimes deceased) real persons rather than completely fictional characters, your publishers would want to be protected against any third party's claims of defamation and violation of his/her privacy and publicity rights, among others.

They do it by asking you, the author, to show them how you came about the material for your story, developed and wrote it, by closely examining the manuscript and background materials for potential legal problems and by asking you to indemnify them against all losses, costs and damages in the publication agreement. Publishers also commonly buy special liability insurance for this purpose. Of course, you could get the person you are writing about to agree in a contract for you to write about him/her and to waive any rights against you and your publishers. But this is not necessary and contacting the subject of your story to ask for such permission can sometimes be counterproductive.

Plenty of "unauthorized" biographies do get published this way once the manuscript is "cleared" and publishers are satisfied with the legal risks they are assuming. Essentially the same rules apply to fictional characters that can be identified or traced back to real people though the legal risk for the publisher is somewhat lower.

Good luck with your story.