We examine the case of payback killings and similar retributive sanctions in the context of a transplant regime such as that existing in Papua New Guinea. This is a post-colonial regime with multiple overlaid legal systems, with significant negative interaction existing between the different regimes. We explain how multiple regimes can co-exist in the context of negative externalities. To explain such an outcome, we provide a simple model for considering the interaction between legal regimes within a single jurisdiction. We demonstrate that, even when the fundamental relationship between such regimes is to behave as substitutes for one another, the existence of negative externalities between the enforcement technologies can result in the withdrawal of enforcement efforts. We term this phenomenon legal dissonance – the situation in which legal regimes interact negatively in their production technologies. This model is then applied to the post-colonial state of Papua New Guinea where we use survey data to identify significant negative production externalities in the enforcement of informal law. We suggest that disorder may be the outcome of too much law.