The challenge is the intersection between the governance provided by folkways and the governance provided by law.

From Doing Bad by Doing Good: Why Humanitarian Action Fails by Christopher J. Coyne. Page 186.

It is important to note that social scientists lack a strong understanding of how to influence underlying customs and beliefs effectively so as to achieve the foundations for desired formal rules. So while we know that customary rules are crucial to the operation of formal rules, we know much less about how to change informal rules to align them with the desired formal rules. This has important implications for efforts by “outsiders,” those who aren’t embedded within the existing rules governing societal interactions, to (re)design rules in order to address root causes by achieving what appears, from their perspective, to be a preferable state of affairs. What seems desirable to outsiders cannot simply be assumed to be desirable to those inside the system due to differing interpretations of the perceived benefits and costs associated with proposed changes.

I think this is a crucial insight. The law cannot govern everything but it must govern that for which it is appropriate. Too great a span and it loses efficiency owing to particularities. Too compressed a span and it loses effectiveness.

Folkways are ideal at the local level for particularities but they do not compass larger heterogenous communities.

The challenge is that intersection between the governance provided by folkways and the governance provided by law.