In Bartz v. Anthropic, Judge William Alsup of the Northern District of California ruled on summary judgment that using books to train a large language model is transformative — "spectacularly so" — serving a purpose fundamentally different from the authors' purpose of being read, and that scanning lawfully acquired books for training was fair use. He held separately that assembling a central digital library from pirated copies was not fair use, and sent that question on toward trial. It was the first US court decision to address AI training data head-on, and it established that how material was acquired could matter more than what was learned from it — becoming a reference point for the copyright cases that followed.