Wikipedia has refused to remove the famous selfie, saying the monkey - and not the photographer - owns the copyright because the animal took it.
In an update to copyright regulations and practices published this week, the US regulator spelled out examples of works that are not eligible for protection.
These include "a photograph taken by a monkey" and "a mural painted by an elephant", says a report in National Journal.
Photographer David Slater was clicking photos of crested black macaques in 2011 when one of the endangered monkeys hijacked his camera and snapped hundreds of pictures.
Among those, there were some stunning images, including a selfie of the macaque that made headlines.