Not sure exactly what you mean, but it’s definitely on the books[1]. There’s also a decent body of case law around copying things you have access to (say, Sony v Betamax).

1: https://codes.findlaw.com/us/title-17-copyrights/17-usc-sect...

fair use is part of copyright law, it’s just defined in a way that what you can claim as fair use is fought over in court.

Fair use comes from Berne Convention §10 (snipet): “It shall be permissible to make quotations from a work which has already been lawfully made available to the public…”

I guess OpenAI and Google use that to be able to build search and training ML-models. Almost all countries in the world is bounded by that.