Depends on the jurisdiction obviously (seems in this case Sweden/EU), but I don't think the author could blanket ban it like that, as research organisations and cultural heritage institutions have exceptions for example. I think news organizations and archivists have exceptions too, but less sure about that.

Besides, I think for it to actually have any effect, it would have to be in a machine-readable format, I'm not sure placing a notice like that in the middle of a HTML document is good enough.

> Art. 4(3) applies only on condition that right holders have not expressly reserved their rights “in an appropriate manner, such as machine-readable means in the case of content made publicly available online”. According to Recital 18, “it should only be considered appropriate to reserve those rights by the use of machine-readable means, including metadata and terms and conditions of a website or a service. […] In other cases, it can be appropriate to reserve the rights by other means, such as contractual agreements or a unilateral declaration.” In other words, Art. 4 right holders may effectively prohibit text and data mining for commercial uses by adding robot.txt type metadata to their content online.

https://copyrightblog.kluweriplaw.com/2019/07/24/the-new-cop...

But maybe the author already have the same notice in a machine readable and of course I'm not a lawyer or anything, so this is just guessing based on what I've learned about the regulations that affect me personally in Spain/EU.