The opinion makes it clear that the justices of the Ninth Circuit think the county has a compelling public health and safety interest in prohibiting guns from places where large numbers of people gather. They argue that the fairgrounds is a "sensitive place" as referenced in Heller (pg. 33 of the PDF).
That was consolation padding to keep them from going en banc and delaying further or pushing the issue again. Since they incorporated, SPECIFICALLY saying Hickman v Block is dead, CCW access will be opened up and the issue will be moot.