Most likely, if you ask ChatGPT to summarize a famous book, it does not need to have ever trained on the book itself. The easiest way for an LLM to create a summary of something is to base its summary off existing summaries created by humans. If it’s ruled in court that ChatGPT is infringing on the copyright of a book’s author only by repeating information it acquired from other summaries created by humans, what implications does that have for the humans who wrote the other summaries?