CCC is a private event and does not fall within the purview of the right to public photography.

Anyway, I don’t go to CCC to take pictures of people - although this is an unfortunate policy because it means that the culture of CCC is not recorded for posterity …

I think it would be a better policy for CCC to require photographers to wear a special easily recognized t-shirt or funny hat, so that they could take pictures of crowds but give non-participants time to dissent.