Apparently the police in Long Beach, California, have a policy that says if a police officer determines that a photographer is taking photos of something with "no apparent esthetic value," they can detain them.
Police Say They Can Detain Photographers If Their Photographs Have 'No Apparent Esthetic Value' | Techdirt
The police are defending this policy, saying that while officers don't have any specific training in what qualifies as "apparent esthetic value," they will stop anyone photographing things they don't consider to be something a "regular tourist" would photograph.