Title 17, Section 107 of U.S. Copyright Law: 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The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.
Beyond the four factors, there are no tangible guidelines for what constitutes a fair use. The courts have deliberately kept the law vague so that fair use cases can be decided on a case-by-case basis.
A fair use of copyrighted materials does not need to meet all four fair use factors. A successful fair use may meet only one factor, or some combination of the factors. For example, a teacher may decide to show an entire film in a classroom setting. This use fails on factor #3, substantiality, because it entails consuming the entire work, and not just a portion. However, the single classroom showing being unlikely to effect the market value of the film (#4) and the educational purpose of the use (#1) both reinforce the right to fair use.
Scholars, artists, and others who wish to use copyrighted material for their own purposes must consider all four factors. Online tools exist to help users make this evaluation. See Fair Use Resources on the left sidebar and the collection of Best Practices on the right sidebar.
The Center for Media & Social Impact has committed itself to ensuring that people in the United States understand their right to selectively use copyrighted material without licensing--a right called fair use, which is protected by the U.S. Copyright Code. Many people believe that fair use standards are too complicated for a layperson to understand, and thus fair use rights are often not exercised. Various groups have come together to create standards for applying to fair use in specific disciplines and to demystify the process.