One of the limitations on the exclusive rights of the copyright holder is found in section 107  of United States Copyright Law. Fair use allows scholars, students, teachers, and others to use works that are still in copyright protection for the purpose of education and criticism. Fair use is intended to be a defense against copyright infringement by allowing people a degree of freedom in using the works of others to create new works. The four factors of Section 107 are a set of guidelines for evaluating whether use of a copyrighted work is 'fair use,' and are not hard and fast rules. For example, in a copyright infringement case, a court would weigh all four factors:
One of the uses specifically mentioned in the purpose clause is education: "the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes." This does not mean that any use is fair as long as it is for educational purposes, as the three remaining factors must also be weighed, but education is specifically mentioned as a favored purpose.
To guide practitioners in their work, some associations and organizations have issued fair use guidelines. Guidelines describe uses that are generally agreed to be fair. It is important to remember, however, that guidelines are not law, they are usually conservative interpretations for a specific context, and as such, may represent minimum guidelines for use. For example, if a guideline recommends using no more than 10% of a copyrighted work, it is not necessarily true that using 15% or 20% cannot be fair.