Re: Hang on a minute…
Copyright confers certain specific rights on copyright holders. However, the right to dictate or limit who is allowed to read (and potentially memorize) the text is not one of those rights. There is nothing illegal about the training per se.
How they got the works being used? - is a separate question. If you can prove that they acquired them illegally, you can prosecute on those grounds. But that's not the AI's fault, any more than if you gave a kid a stolen book for her birthday.
But in either case, if the reader goes on to regurgitate the text - and particularly if they accept payment for doing so - that's a clear and egregious violation.