Unauthorized reposting of deleted copyrighted posts

[Homer]

If the author of a series of offically copyrighted posts on a public forum delets his posts and the thread he started where the copyrighted posts were contained; is it a violation of copyright law for other forum members to re-post copies of the original thread and copyrighted posts to new and different threads without permission of the original author? If the original author sends a request for his unauthorized copyrighted works to be removed and the new thread starter refuses, what recourse does the original author have? What responsibility does the web forum owner and administrators have to see that the unauthorized copyrighted works are not posted or if posted then removed once notified by the original author?