Perhaps the most well-known case that has gone to court related to Harry Potter, was Warner Bros. Entertainments Inc. and J.K. Rowling, Plaintiffs, v. RDR Books and Does 1-10 Defendants (575 F.Supp.2d 513). The full text of the judgment of this case is available in any standard legal database.
Many articles have been written addressing intellectual property questions raised by fan fiction and other derivative works created in response to Harry Potter. Search HeinOnline, SSRN, or other sources for articles on copyright, trademark, or other implications of intellectual property laws.