[threatofrain]

There are informal contracts and their enforcement occurs through extra-legal means. For example, there is a general compact not to murder in any society. So when revenge happens after murder, there's an informal moral understanding and cushion of social sympathy and forgiveness for vengeance, even if vengeance is typically illegal. In other words, if you break the agreement of peace then you should expect payment in violence.

For entities as large as the state, I think there is an informal contract for people not to engage in anarchistic or revolutionary violence until their living circumstances becomes untenable. The degree to which their circumstances are understood as unjust will interact with the response they get from society.

IMO such agreements must be informal and fuzzy, and a lot of peace is maintained through these extra-legal structures.