In our group, the friendship is based on respect, love and equality so I think that no one controls the other people
therefore there is no social control mechanism.We only use two laws. first don´t steal the friend´s girlfriend and tha second law is "what happens in the jungle, stays in the jungle".In case of one of the person in the peer group has a strange behavior, we think that the most important thing is talk with this person about this behavior.
I think the most important thing to keep a group is have things in common and do things that you all enjoy.
Friends come first.