Well, you are in a small, enclosed community that nobody can ever leave. How long is this ship going to be traveling? If it's a very long time (eg a colony ship, or a Voyager-esque lost ship), expect things to get really messy. In particular, resources are at a premium. If somebody commits a heinous crime, life in prison is out of the question: There will be capital punishment. If it's long enough that you expect new generations to be born, then things start getting really dystopian.