No more than any other meetup in public.

Any rules are more like do not wear bondage gear next to a playground at a local park.

(This isn’t as clear as you might think. No one really bats an eye at superhero costumes. A leather catsuit with a tail, chains, and pup hood does not have the same reaction.)

They usually aren't that structured and for some of them they don't really even have someone who runs the event, it's just self perpetuating that people know other people will be at this venue this day. So any kind of rules would just be the rules of the pub or venue itself.