CHAPTER 9. Fair Use
Fair use is a copyright principle based on the belief that the public is entitled to freely use portions of copyrighted materials forpurposes of commentary and criticism. For example, if you wish to criticize a novelist, you should have the freedom to quote a portion of the novelist's work without asking permission. Absent this freedom, copyright owners could stifle any negative comments about their work.
Unfortunately, if the copyright owner disagrees with your fair use interpretation, the dispute will have to be resolved by courts or arbitration. If it's not a fair use, then you are infringing upon the rights of the copyright owner and may be liable for damages.
http://fairuse.stanford.edu/Copyright_and_Fair_Use_Overview/chapter9/index.html