What Is Fair Use?

Fair use is a defense to copyright infringement that turns on the particular use. The Copyright Act identifies four factors, which courts weigh together in context: the purpose and character of the use; the nature of the copyrighted work; the amount and significance of the portion taken; and the effect of the use on the potential market for or value of the work (17 U.S.C. § 107). Commercial use is not automatically disqualified, and educational use is not automatically permitted. Fair use has no universal safe number of words, seconds, or pixels. Attribution alone does not supply permission, and changing a work does not by itself make the use fair.

The first appellate fair use ruling on AI training is Thomson Reuters Enterprise Centre GmbH v. ROSS Intelligence Inc., No. 25-2153 (3d Cir. Sept. 29, 2026). The Third Circuit held that ROSS's use of Westlaw headnotes to train a competing legal-research tool was not fair use. Only the second factor, the nature of the work, favored ROSS, and only slightly; the court found the use highly commercial and minimally transformative, found that ROSS took more than it needed because the underlying opinions were freely available, and treated the market for licensing headnotes as AI training text as a derivative market the owner may reserve. The ruling is deliberately narrow: ROSS's system retrieved existing texts rather than generating new ones, so whether training a generative model on copyrighted material is fair use remains undecided at the appellate level. The decision binds district courts within the Third Circuit; for Texas courts it is persuasive only, since the Fifth Circuit has not addressed fair use in AI training.

Pinpoint: 17 U.S.C. § 107. Related term: Fair Use.

Sources.

• 17 U.S.C. § 107: limitations on exclusive rights, fair use. law.cornell.edu

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