While, I'm not a public official, here's my take on this issue. While AA meetings are considered anonymous, meeting in a public place funded by taxpayers creates an unreasonable expectation of privacy. So the group would either have to meet in doors where there is more of a reasonable expectation of privacy and rules or understand that meeting at a public park - even if the pavilion is rented doesn't prevent others from using the rest of the park or taking photos. However, if someone believes they are being targeted while they are at a park, they can call police. There are stalking laws that may come into play.