Folsom v. United States is a Supreme Court case that dealt with the issue of copyright infringement. The defendant, Folsom, had published a book about George Washington using letters written by him without obtaining permission from the plaintiffs who owned the copyrights to these letters. The court ruled in favor of the plaintiffs and established an important precedent for future copyright cases: when determining whether or not something constitutes as fair use (a concept that allows limited use of copyrighted material without requiring permission), courts must consider factors such as how much of the original work was used and whether its usage would potentially harm sales or value of said work. This ruling has significantly influenced American intellectual property law ever since.

The dissenting opinion in the Folsom v. United States case argued that the defendant's actions did not constitute copyright infringement. The dissenting justices believed that while Mr. Folsom had indeed used portions of George Washington's letters for his own publication, he had done so in a manner consistent with fair use principles and without infringing on any exclusive rights held by the plaintiff (the United States). They contended that Mr. Folsom’s work was transformative rather than derivative, as it added new insights and understanding to the original material through careful selection, arrangement, and commentary - all of which required considerable intellectual labor and judgment on his part. Therefore, they concluded that such usage should be protected under copyright law instead of being penalized.