It sounds as if the authors of a Dr. Seuss-"Star Trek" mashup will have to boldly go to trial on copyright infringement—without their fair use defense.

Argued before the U.S. Court of Appeals for the Ninth Circuit Monday, Dr. Seuss Enterprises v. ComicMix was framed by some amici curiae as a prime opportunity to apply fair use principles to the increasingly popular art of mash-ups. But the arguments ended up turning more on traditional principles of fair use, and not in a way that favored the authors of "Oh, the Places You'll Boldly Go," a book that places "Star Trek" characters and props in Dr. Seuss settings.

Hedging his bets, attorney Dan Booth of Dan Booth Law argued that "Boldly Go" is both a parody of "Oh, the Places You'll Go" and a mash-up. "It's both at once. That is an innovative form that combines elements from two different sources and puts them in dialogue with one another," he told the judges. "The test should be the same for a parody."

"That seems to me to be somewhat an after-the-fact justification of why they chose Dr. Seuss," Judge M. Margaret McKeown told Booth. "If you go back in the record, and the creators of 'Boldly' are looking around for what should they use, and how should they copy it, slavishly, and that sort of thing," she said. Eventually they hit on "Oh, the Places You'll Go."

Dr. Seuss Enterprises, or DSE, is represented by DLA Piper. It contends that science fiction author David Gerrold, illustrator Ty Templeton and ComicMix founder Glenn Hauman picked "Oh, the Places You'll Go" because they believed a "Star Trek" version would make a great holiday or graduation gift, exactly the market the Dr. Seuss book plays to.

DSE has licensed other authors to create "Oh, The Things You Can Do That Are Good For You" and "Oh, the Places I've Been! Journal." But the ComicMix authors plunged ahead unlicensed, even though they acknowledged in their Kickstarter campaign that "we may have to spend time and money proving [fair use] to people in black robes."

"'Boldly' is just a 'Star Trek'-flavored clone" of "Oh, the Places You'll Go," DLA partner Stanley Panikowski told the Ninth Circuit on Monday.

The authors argued, and U.S. District Judge Janis Sammartino of San Diego had agreed, that while they borrowed liberally from the Seuss book, they rewrote all of the text and reframed the images from a unique "Star Trek" viewpoint. ("You can get out of trouble, any that's knotty/because in a pinch you'll be beamed out by Scotty," the book reads at one point.)

Booth tried to pick up where Sammartino had left off. "The book is constantly pointing out the individualist and narcissistic character of 'Oh, the Places You'll Go,'" he told the Ninth Circuit. "The Star Trek Enterprise, and the Star Trek crew, is a team effort. … Group support and communion rather than individuality."

McKeown said she didn't see how that amounts to parody. Plus, she pointed out, "when they said parody, they also said, 'Well, maybe those people in black robes would disagree with us.'"

"That's true," Booth acknowledged. "They were quite tongue-in-cheek about that. But they made it very clear that their opinion was this was fair use, this was a parody, this is a transformative work."

McKeown also sounded skeptical of the mash-up argument. "The district court seemed to take the position that if you take existing expression and intersperse it with some new expression, then all of a sudden you have a transformative work," McKeown said. "That is a definition of transformative and fair use that I certainly haven't seen before."

Booth insisted that "if you are using underlying materials, and using them in a different way every time as thoroughly as the defendants did," then you have transformed it.

Booth appeared to make some modest headway with McKeown, who told him she'd let him exceed his allotted time "because you've been making some very interesting arguments."

It sounded as if the case would come down to whether the ComicMix authors failed to prove their book wouldn't harm the market for "Oh, the Places You'll Go." Panikowski argued—and the Ninth Circuit judges seemed to agree—that Sammartino had erred in placing the burden of proof on DSE, because the burden of proving fair use always falls on the defendant.