In an unusual move, the Andy Warhol and Robert Rauschenberg foundations have petitioned to file a "friend of the court" brief in the ongoing copyright case Patrick Cariou v. Richard Prince. Their argument: the intellectual content and aesthetic meaning of works of art are not always visible to the naked eye without art-historical context.

"It is a long-held tenet among art historians, curators and many other cultural commentators that adequate assessment of an artwork's meaning is not limited to what can be seen and felt by the five senses," the foundations' statement says.

"The notion that context informs meaning isn't a radical one, and certainly not to people in the art world," New York attorney Virginia Rutledge, counsel for the Warhol Foundation, who co-authored the brief, told A.i.A. by phone. "And from a copyright perspective, that notion is perfectly compatible with the concept of transformative fair use. What may seem novel here is the assertion that the visual alone is an inadequate measure of new meaning, and thus whether an infringement has taken place."

Signatories to a supporting letter include museums such as the Art Institute of Chicago, the Dia Art Foundation, the Los Angeles County Museum of Art and New York's Museum of Modern Art.

"I think the museums correctly see this case as putting at risk all appropriation art and they want to undo the damage," New York art lawyer Donn Zaretsky told A.i.A. by e-mail.

The case concerns Prince's "Canal Zone" series of paintings (2008), which incorporate photographs by French photographer Patrick Cariou from his 2000 book Yes, Rasta (Powerhouse), produced for a show at New York's Gagosian Gallery. In 2009 Cariou brought a copyright infringement suit against Prince, Gagosian Gallery, Lawrence Gagosian and catalogue publisher Rizzoli. In March 2011, U.S. district judge Deborah Batts ruled against Prince and ordered the defendants to destroy remaining copies of the catalogue and unsold paintings that make use of Cariou's photographs. That decision was largely overturned in April, with the exception of five paintings that, the court concluded, are not obviously transformative and thus must be reevaluated for claims of fair use.

"It's unusual for an amicus brief to be filed in a district court," Rutledge said. "But the appellate decision made it clear that the district court needed more evidence before it could make its determination on the remaining five paintings, and we felt it important to offer an argument that other arts organizations believed should be emphasized as well."

The Second Circuit's decision requires Batts to determine whether a "reasonable observer" would perceive Prince's paintings to be "transformative" of Cariou's photographs, according to the brief. As Rutledge put it to A.i.A., "why shouldn't the audience that undeniably finds Prince's work to be different from Cariou's count among those reasonable observers?"

Daniel J. Brooks, counsel for Cariou, declined to comment when reached by phone today, saying he had not yet read the foundations' filing.

There is no definite schedule by which the court would respond to the foundations' petition, Rutledge told A.i.A.

"I think this just shows how unhelpful the Second Circuit decision in the case was," Zaretsky said. "No one knows what the hell it meant. Prince's lawyers have taken the position it means the fair use issue has to go to a jury on the five remaining works. But the museum community—though it's entirely on Prince's side—is arguing here that the district court can decide the fair use question after considering additional evidence from critics, scholars, and so on. It's a big mess."