This page in a nutshell: Delete libelous material when it has been identified.
Look up in Wiktionary, the free dictionary. libel
The goal of
Wikipedia is to create an encyclopedic information source adhering to a neutral point of view, with all information being referenced through the citation of reliable published sources, so as to maintain a standard of verifiability. 
It is the responsibility of all contributors to ensure that the material posted on
Wikipedia is not defamatory.
Wikipedia policy to delete libelous material when it has been identified. Contact instructions for subjects of libel
If you believe that you are the subject of a libelous statement on Wikipedia, please:
us with details of the article and error. E-mail See also Policies References External links How to avoid libel and defamation (2004)—Information from the BBC for contributors to its defunct community website, Action Network, based on the English law of libel, which differs considerably from U.S. law. Note that Victoria Gillick actually lost her libel case, the reverse of what this claims. Millward, David, , as accessed Feb. 1, 2011. Victoria Gillick 'broke' after losing libel case, in The Telegraph, Nov. 20, 2000, 12:00AM GMT, section UK News Once it's on the Web, whose law applies? Internet policy – Jurisdiction Defamation FAQ at Chilling Effects Clearinghouse