I assume you have some standards of behavior, though, right? If a member of your group, say, punched another member, you’d probably kick him out, right?

If so: you have a code of conduct, you just don’t have a _written_ code of conduct. You’re relying on the relative homogeneity and shared context of the group to know and follow the unwritten rules.

This tends to work ok for smaller more homogenous groups with shared social values. But unwritten rules fail for people on the margins, and falls apart at scale.