After Patrick Cariou's legal team filed its appellate brief recently in the epic battle the photographer is fighting against appropriation artist Richard Prince and Gagosian Gallery, the Web was awash in analysis of the case's meaning for the art world and discussion of the amicus briefs filed by various interested parties on behalf of one side or the other. But the one thing that few have discussed is the rather strong argument made by Internet giant Google's legal team that the decision poses a major threat to not only to a few key Google properties that depend on fair use like Blogger and YouTube, but its entire raison d'être: Internet search.

Before going further it should be noted that amicus briefs, or "friends of the court," have little to do with the case itself and are unlikely to affect the outcome. They are just notes to the judges deciding the case, written by interested but uninvolved parties, letting the court know how its decision could affect future cases. Those that filed in favor of Prince — the Warhol Foundation, as well as the Association of American Museum Directors and its museum co-signors (including the Met and MoMA) — want to prevent similar lawsuits against appropriation art in the future. Getty Images and Corbis, both of which filed a joint brief in favor of Cariou, want to make sure their right to sue for copyright infringement is protected.

Meanwhile, Google filed a neutral brief (it was not in favor of Prince, as has been previously reported) objecting to the specific language used by the district court judge finding in favor of Cariou. The document written by the Google legal team says that the opinion "diverges in dangerous ways from the mainstream of fair use analysis." Specifically, it refers to two passages from the original Prince v. Cariou opinion, which notes that "all of the precedent that this Court can identify imposes a requirement that the new work in some way comment on, relate to the historical context of, or critically refer back to the original works," and goes on to say that "Prince's Paintings are transformative only to the extent that they comment on [Cariou's] photos."

This particular argument, Google says, is "simply not the law." The opinion as it stands imposes a very narrow definition of fair use, which requires that a new work that uses content from a copyrighted work be "transformative." Specifically, it has to transform the old work by commenting on or criticizing the original work. If this were the law, Google would have a big problem. The company uses a lot of copyrighted work (notably, a huge chunk of the Internet) without transforming it at all. In order to show webpages that appear on its search page, it basically trolls the Web, copying all the pages it finds in order to index the web's content. When it does that, it copies without comment or criticism — if it did, the search function wouldn't be helpful. Thus far, the courts have ruled in favor of Google and similar defendants, saying that the way search functions index the web qualifies as fair use because "large-scale copying of works in digital form was required to achieve a socially useful goal."

However, the distric court in the Cariou case defined a much, much narrower scope for fair use that, if it stands up on appeal, might hand every every indexed Web site cause for a copyright infringement lawsuit. Even though the search function is largely a useful digital tool that brings traffic to Web sites and its unlikely that anything short of a Supreme Court ruling could actually bring it down, the language of this decision does leave Google vulnerable to lawsuits from any old Joe with a copyrighted Web page and an opportunistic attitude. The probability that Google would actually be faced with millions of lawsuits is fairly slim — after all, Google's search index is helpful to most sites and brings in a fair amount of traffic. However, it's not negligible, and the requirement that a work must be transformative in order to be fair use puts Google — and most of the Internet — in a very precarious position indeed.