Google’s scanning of books does not meet the legal definition of “transformative,” creates potential harm to authors and other copyright holders, and is not protected as fair use under the law, the Authors Guild argues in a brief filed this week in New York federal court.

“The only thing ‘transformative’ about Google’s display of snippets of in-print books is that it transforms online browsers of book retailers to online users of Google’s search engine. Google ‘transforms’ Amazon customers into Google ad-clickers,” according to the brief.

Whether Google’s mass digitization of copyrighted material qualifies as fair use is the central issue now facing the court in the long-running legal dispute between the search engine giant and the Guild. A decision on fair use issues will influence whether the case should proceed as a class action lawsuit.

In a brief also filed this week, Google maintains that its scanning of copyrighted material is transformative, and actually helps authors by making their books easier to find and benefits the public by rendering information more accessible.

The Guild rejects the characterization of Google’s library-scanning project as anything other than a commercial enterprise intended to give it an advantage over other search engines and increase ad revenue–all while putting authors’ valuable property at risk.

The Guild’s brief points out the threat of piracy created by Google’s online distribution of book content. “One need only pick up a daily newspaper to appreciate how serious this security risk is. Stories of break-ins, hacking and theft appear almost daily.”

The current focus on fair use resulted from an appeals court decision in July. The judge vacated a class certification ruling in The Authors Guild vs. Google, saying issues of fair use had to be decided before determining whether authors should be treated as a class in the case. If Google’s fair use defense requires a book-by-book analysis, then this would weigh against class certification. If a fair use ruling can be made more broadly, then judicial economy is more likely to weigh on the side of class certification.

As the court weighs the legal issues, it’s already clear that Google’s unauthorized scanning of books creates a hazard for every author.