Digging and sifting through the events section to find "it" exceeds my BF forensic capabilities. I would be surprised if any non racing event registration fine print about participant requirements specifies words more descriptive than "helmet required," with no explanation and racing events might specify "CPSC certified helmet required."

I would not be surprised if questioned about a helmet requirement for event participants, event organizers might respond with a rote response "Our insurance requires it" whether that statement is true or not.
I would be very surprised if any event registration (or insurance company) specified a minimum helmet rating or number of stars assigned by VTI except perhaps a CPSC certification for racing events.

I would be even more surprised if any event official ever checks the ratings or certification labels of the helmets being worn by the event participants.