In an update to the post mentioned here, David Post points to a post by the University of Chicago's Randy Picker that says the real question in the Fairey case is "what was copied from the Garcia work, as opposed to taken from the original event as accessed through the Garcia work. Copyright is all about the former and not the latter. In this framework, ... it will be incumbent upon Garcia to establish precisely what Fairey copied ... other than the underlying event. ... Garcia will find it easier to make that case if Fairey has physically worked from the original image and remixed it. Much harder, I think, if Fairey has merely looked at the Garcia photograph and then created his own image. ... [C]opyright proper doesn’t bar Fairey from accessing that original event through the Garcia photograph."
Also, Bruce Boyden has the second in a series of posts on the case, this one looking at the question who owns the allegedly infringed photo (note that, in the passage quoted above, Picker assumes it's Garcia, the photographer, and not the AP): "If Garcia is correct, there aren’t any signed agreements one way or the other here, so it all comes down to whether he was an 'employee' at the time he took the photo."