The Supreme Court on Monday declined (PDF) to hear a challenge from the Authors Guild and other writers claiming Google's scanning of their books amounts to wanton copyright infringement and not fair use.

The guild urged the high court to review a lower court decision in favor of Google that the writers said amounted to an "unprecedented judicial expansion of the fair-use doctrine." (PDF)

At issue is a June decision (PDF) by the 2nd US Circuit Court of Appeals that essentially said it's legal to scan books if you don't own the copyright. The Authors' Guild originally sued Google, saying that serving up search results from scanned books infringes on publishers' copyrights even though the search giant shows only restricted snippets of the work. The writers also claimed that Google's book search snippets provide an illegal free substitute for their work and that Google Books infringes their "derivative rights" in revenue they could gain from a "licensed search" market.

The Supreme Court let stand the lower court opinion that rejected the writers' claims. That decision today means Google Books won't have to close up shop or ask book publishers for permission to scan. In the long run, the ruling could inspire other large-scale digitization projects.

Fair use is a concept baked into US copyright law, and it's a defense to copyright infringement if certain elements are met. The US Copyright Office says the defense is decided on a case-by-case basis. "The distinction between what is fair use and what is infringement in a particular case will not always be clear or easily defined. There is no specific number of words, lines, or notes that may safely be taken without permission. Acknowledging the source of the copyrighted material does not substitute for obtaining permission," the US Copyright Office says. There are, however, at least four factors that judges must consider when deciding fair use: the purpose of use, the nature of the copyrighted work, the amount and substantiality of the portion taken, and the effect of the use upon the potential market.

The Supreme Court did not comment in its order other than to say that Justice Elena Kagan did not participate.

Google, for its part, urged the justices to side against the writers because, in the end, their works would be more readily discovered. "Google Books gives readers a dramatically new way to find books of interest," Google's brief said. (PDF) "By formulating their own text queries and reviewing search results, users can identify, determine the relevance of, and locate books they might otherwise never have found."

Unlike other forms of Google search, Google does not display advertising to book searchers, nor does it receive payment if a searcher uses Google's link to buy a copy. Google's book scanning project started in 2004. Working with major libraries like Stanford, Columbia, the University of California, and the New York Public Library, Google has scanned and made machine-readable more than 20 million books. Many of them are nonfiction and out of print.