The photog -- not our guy -- claims he and a pack of shutterbugs were "legally standing on public property" outside of Kate's L.A. home back in 2008 when Kate and Baron arrived.
According to the suit, the photog claims Baron, "apparently unnerved by the media attention, picked up a dirt clod and threw it" ... striking the pap in the face and eyes.
The photog claims he suffered some serious damage to his eyeball -- and wants Baron to fork over more than $25,000 to make things right.
