There is a distinction that must be made that very few people do, but thankfully the courts seems to grasp:
Training on copyright is a separate claim than skirting payment for copyright.
Which pretty much boils down to: "If they put it out there for everyone to see, it's probably OK to train on it, if they put it behind a paywall and you don't pay, the training part doesn't matter, it's a violation."
Whether it’s legal slash fair use to train on copyrighted material is only one of the questions currently being asked though. There’s a separate issue at play where these companies are pirating the material for the training process.
By comparison, someone here brought up that it might be transformative fair use to write a play heavily based on Blood Meridian, but you still need to buy a copy of the book. It would still be infringement to pirate the e-book for your writing process, even if the end result was legal.
If they would buy material at a large scale, the seller might require them to sign a contract that requires royalty if the material is used for training an AI. So buying legally is a way to put yourself into a trap.
The only thing I've been able to find is the note that since copyright is federal law, state contract law actually can't supersede it, to wit: if you try to put a clause in the contract that says the contract is void if I use your work to make transformative fair-use works (or I owe you a fee), that clause is functionally unenforceable (for the same reason that I don't owe you a fee if I make transformative fair-use works of your creations in general).
So if I download copyrighted material like the new disney movie with fansubs and watch it for training purposes instead of enjoyment purposes it's fine? In that case I've just been training myself, your honor. No, no, I'm not enjoying these TV shows.
Because it's important to grasp the scale of these copyright violations:
* They downloaded, and admitted to using, Anna's Archive: Millions of books and papers, most of which are paywalled but they pirated it instead
* They acquired Movies and TV shows and used unofficial subtitles distributed by websites such as OpenSubtitles, which are typically used for pirated media. Official releases such as DVDs tend to have official subtitles that don't sign off with "For study/research purpose only. Please delete after 48 hours" or "Subtitles by %some_username%"
OpenSubtitles is almost exclusively used with pirated media. Official copies come with official subtitles. OpenSubtitles itself is legal, but that's not the point at all.
Training on copyright is a separate claim than skirting payment for copyright.
Which pretty much boils down to: "If they put it out there for everyone to see, it's probably OK to train on it, if they put it behind a paywall and you don't pay, the training part doesn't matter, it's a violation."