The line between “fair use” in copyright law and outright theft has often been unclear, but a recent U.S. District Court ruling drew the line on a case involving Equals Three Studios and viral-video aggregator Jukin Media. Jukin accused Equals Three of illegally taking dozens of clips for use in its own YouTube show. Equals Three sued Jukin, saying its actions were protected by fair use, and that Jukin’s takedown deprived it of ad revenue. The Court’s ruling sides with Equals Three on all but one of the videos under consideration.

According to Variety, Judge Stephen V. Wilson of the U.S. District Court for the Central District of California wrote in his October 13 decision that, “Equals Three’s use of Jukin’s videos is admittedly commercial. Nevertheless, the commercial nature of the use is outweighed by the episode’s transformativeness.”

“Transformative” appears to be the key deciding factor, but nowhere is that defined, notes Variety.

Wilson’s ruling continued that because Equals Three episodes comment or criticize Jukin’s videos, whether or not they are parodies, they are allowed under fair use provisions. He gave the example of the Equals Three episode “Drunk Babies” that used part of Jukin’s video “Groom drops bride,” but also featured the show’s host commenting on the Jukin video clip.

“Transformative” came up again in a ruling by the 2nd Circuit Court of Appeals, which upheld a lower court decision by applying that term to Google’s book-scanning service, which makes millions of books publicly searchable. A similar definition of fair use was supported by the 9th Circuit Court of Appeals, which ruled that a woman’s YouTube video of her children dancing to Prince’s “Let’s Go Crazy” was a fair use that Universal Music should not have taken down.

Equals Three is of course happy with the recent ruling, but Jukin Media preferred to focus on the single video that the court said did not fall under fair use. Jukin, which has an 11-member team that looks for and licenses viral videos, says it plans to review the rest of the court’s decision.

Related:
Google’s Digital Library Wins Court of Appeals Ruling, The New York Times, 10/17/15