• Actual text in US Code, Title 17, section 107 (original source)
• Additional precedent ('tranformative')
• YouTube videos and US law
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 —
(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.
This is an additional factor, established by precedent (see list of cases using it), that helps determine if citation can be considered fair use. This criterion examines
' the degree of transformation accomplished by the new work by determining whether the new work has a different purpose or different character than that of the original copyrighted work. For example, does a new work accomplish a transformative purpose by adding something entirely new to the copyrighted work or does the new work only supplant the original copyrighted work?'
'What constitutes a “transformative work” is not subject to exacting definition. However, as a general rule, if the new work “merely supersedes the objects of the original creation,” it is not transformative, but if it “adds something new, with a further purpose or different character, altering the first with new expression, meaning, or message,” it is transformative.
Four of the five points in US federal law that support fair and scholarly use of copyrighted material are codified under Section 107 of Title 17 of the US Code. The fifth point (transformative chanracter) is established by legal precedent. You can check the validity of your counter-claim against these five points by answering five questions.