The case stems from an incident in 2011, when British photographer David Slater, on a visit to the Tangkoko Reserve in Sulawesi, Indonesia, put down his camera and walked away. When he looked back, a crested black macaque monkey was examining the camera, looking at a reflection in the lens, and, as Slater described it, making funny faces before snapping the shutter.

The photos became a hit on social media, while Slater went on to publish them in a 2014 book, "Wildlife Personalities." That prompted the nonprofit People for the Ethical Treatment of Animals to file suit on behalf of the monkey, whom they named Naruto, claiming the right of a thinking nonhuman to legal ownership of the creature's own creative work.

The suit relied on a 2004 ruling by the Ninth U.S. Circuit Court of Appeals in San Francisco that allowed animal-rights supporters to sue on behalf of whales and dolphins in opposing — unsuccessfully, as it turned out — Navy sonar testing.