In legal situations, you don't have a "core argument". You have as many parallel arguments as possible, even if they are somewhat contradictory. One argument is

In legal situations, you don't have a "core argument". You have as many parallel arguments as possible, even if they are somewhat contradictory. One argument is that the photos are un-copyrightable (public domain), as they are not the creative works of a human. Another argument is that if the photos are copyright, it's "fair use". He's keeping one foot on both boats, in case one of them sinks.