Good grief, I couldn’t believe it and so I looked it up. It was legal because they got a permit.
Exception:
Events with permits (e.g., World Naked Bike Ride) may be allowed because organizers obtain special permissions.
Something else I learned today 
California has no statewide ban on simple public nudity.
Being naked is only illegal if it is lewd, sexual, or meant to offend.
Indecent Exposure – Penal Code §314
A crime only if:
-
Genitals are exposed willfully,
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With sexual intent (arousal, gratification, or to offend).
Lewd Conduct – Penal Code §647(a)
Covers sexual acts in public, not simple nudity.
So:
A nude person with no sexual intent is not violating state law by default.
I knew there were nudist camps and beaches, but assumed they were privately owned.
Well my cycling group won’t be part of it. The family jewels may not get used as often, but we still want to protect them.
This is an international event, and I’m just wondering why naked? At least I’ve learned if I ever see a naked person in public not to call the police unless they are playing with their self. 
Damn that would chafe!!!
I’d be happy to give a little TLC to any of these riders (Oh how I miss the 70’s and 80’s)
This happened a few years ago. Supposedly she took her own life, months after being arrested for pleasuring herself with a sex toy on the beach.
Someone had called the Police to report this woman’s behavior.
