Yes. See https://en.wikipedia.org/wiki/Feist_Publications,_Inc._v._Ru.... - "sweat of the brow" does not confer copyright, only creativity does.

More to the point: the reason you find so many people advocating for pirating textbooks specifically, is because textbooks have often been used by authors/institutions/publishers to fleece students:

https://en.wikipedia.org/wiki/Textbook#New_editions_and_the_...

> Some textbook companies have countered [the second hand market] by encouraging teachers to assign homework that must be done on the publisher's website. Students with a new textbook can use the pass code in the book to register on the site; otherwise they must pay the publisher to access the website and complete assigned homework.

> Harvard economics chair James K. Stock has stated that new editions are often not about significant improvements to the content. "New editions are to a considerable extent simply another tool used by publishers and textbook authors to maintain their revenue stream, that is, to keep up prices."

Students can tell when they're being scammed, and are more than happy to go to war with scammers such as these.