17 U.S.C. § 107 - U.S. Code - Unannotated Title 17. Copyrights § 107. Limitations on exclusive rights:  Fair use

Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright.  In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include--

The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.