The charity maintains that if an animal takes a photograph, the image legally belongs to that animal.
Photographer David Slater thought that he had captured the photograph of a lifetime when a curious monkey managed to take its own picture using his camera in the Indonesian jungle back in 2011.
Unfortunately however the animal charity Peta has since insisted that Slater doesn't really own the copyright to the image because he didn't actually take it - the monkey did.
Back in January a US court ruled that the copyright of the image couldn't be owned by a monkey, but now Peta has appealed against this decision by insisting that it should belong to the animal.
"Had the monkey selfies been made by a human using Slater's unattended camera, that human would undisputedly be declared the author and copyright owner of the photographs," the charity wrote. "Nothing in the Copyright Act limits its application to human authors."
If the appeal succeeds it will be the first time an animal has ever been granted copyright ownership.
"It's nothing to do with the monkey, they just care about the promotion," said Slater. "They are going on the idea he [the monkey] owns the copyright, which is clearly absolutely ridiculous."
Whether Peta will actually succeed in overturning the original verdict however remains to be seen.