The story of the artistically-inclined macaque first made its way around the web in 2012. According to David Slater, the British photographer whose camera was "borrowed", the monkey hijacked the camera while the photographer was on a trip to the Indonesian jungle in 2011, and took tons of pictures, including the selfie.
That mischievous monkey also took this photo. I believe Slater is the one on the left:
Noting that Slater had registered the copyright to the selfie in his own name, experts opined at the time that the photos taken by the monkey were probably in the public domain because the creator was a monkey, and thus technically could not claim a copyright.
That opinion was seconded a few weeks ago when Wikimedia, the non-profit behind Wikipedia, revealed that they had declined to remove a copy of the famous selfie which had been uploaded by a user. The organization had received a DMCA notice and after much internal debate decided not to take it down. In their opinion the image was in the public domain.
And now the matter has been settled by the US copyright office - in the US, at least. According to The Telegraph, there is a clause in that country's copyright law where the photographer might be able to claim that he owned the copyright:
In the UK, under the Copyright Designs and Patents Act 1988, a photographer can claim rights over an image even if he or she did not press the shutter button if the results are their “intellectual creation” – for example, they came up with the concept of a monkey taking a “selfie”.
However, such a case has never been tried in court and the outcome would be uncertain.
This probably won't help Slater; he has already admitted that the monkey stole the camera without his permission. In short, he didn't intend to create the circumstances for the monkey to take the photo, so he can't claim that the monkey was working for him.