The role of third parties in norm enforcement in customary courts among the Enga of Papua New Guinea.

Cultural norms are key to cooperation in human societies. How they are regulated, maintained, and adapted to the change remains a matter of debate. Humans have dispositions for both retributive and restorative justice; recent focus has been on third-party punishment, punitive sanctions by those not directly harmed, as key for norm enforcement. However, punishment does not engage the essential proficiencies and emotions critical to cooperation in small-scale societies with high dependence on collective action, sharing, and exchange. Third-party participation in norm enforcement is examined with data from a 10-y study among the Enga of Papua New Guinea. The Enga have a plural justice system with formal courts practicing retributive justice and customary courts applying restorative measures. Most cases are brought to customary courts. Drawing on observations from 333 village customary court cases concerning assault, marriage, land, and property violations, third-party engagement outside of and during customary court hearings is analyzed. Results show that all sides are heard, restoration is prioritized, and third-party punishment is rare; rather, third parties help with compensation to reintegrate wrongdoers and resolve conflicts. Repeated offenders and free riders receive ever less community support. Third parties contribute substantially both during and outside of customary court sessions to help kin, pursue economic agendas, or gain reputation. They also act generously to build a strong community. Emphasis is on amends to the victim for fairness, not punishment of the offender. Broad third-party participation is maintained throughout times of rapid change to adapt while supporting essential structures of society.