The battle over now-famous selfies taken by a macaque monkey will head back to a court in the US.
The Court of Appeals for the Ninth Circuit in San Francisco will hear arguments on whether an animal can own the copyright to a photograph on Wednesday.
The proceedings will be broadcast online.
A federal judge last year ruled that the monkey cannot be declared the photos' copyright owner, saying that while Congress and the president can extend the protection of law to animals as well as humans, there is no indication that they did so in the Copyright Act.
The lawsuit filed in 2015 by People for the Ethical Treatment of Animals (PETA) sought a court order allowing the group to administer all proceeds from the photos for the benefit of the monkey, which it identified as Naruto, a free-living crested macaque from Indonesia.
PETA says Naruto has been accustomed to cameras throughout his life and took the selfies when he saw himself in the reflection of the lens.
The animal rights organisation said the monkey drew the connection between pressing the shutter release and the change in his reflection, and made different facial expressions while pressing the shutter release.
The photos of the monkey with a toothy grin were taken in 2011 in Sulawesi, Indonesia, with an unattended camera owned by British nature photographer David Slater.
Mr Slater says the British copyright obtained for the photos by his company, Wildlife Personalities Ltd, should be honoured worldwide.
PETA sued Mr Slater and his San Francisco-based self-publishing company Blurb, which published a book called Wildlife Personalities that includes the "monkey selfie" photos.
If successful, this will be the first time that an animal is declared the owner of property, instead of being declared a piece of property himself, PETA lawyer Jeffrey Kerr said.
"When science and technology advance, the law adapts," Mr Kerr said.
"There is nothing in the Copyright Act limiting ownership based on species, and PETA is asking for an interpretation of the act that acknowledges today's scientific consensus that macaque monkeys can create an original work."