Should law keep pace with society?

Most modern societies have adopted centralized rules of legal punishment to promote collaborative behavior. Among other advantages, a centralized institutional punisher can unilaterally decide the rate at which legal rules evolve relative to the social behavior being regulated. Legal and political theorists disagree over whether or not law should evolve more slowly than social behavior. Some scholars argue that slower evolution promotes the stability of tradition. Others argue that more frequent adaptation permits law to remain relevant to contemporary decision-making. We investigate this question by modeling the co-evolution of law and social norms in a public goods game with centralized punishment. We vary the relative update rate of legal rules–the rate at which the State updates the legal punishment strategy relative to citizens’ updating of their contribution strategy–to observe the effect of such variance on citizen cooperation. We find that when States have unlimited resources, legal rules that evolve more slowly will maximize citizen cooperation: slower relative updating forces citizens to adapt to the State’s legal punishment rules. When States depend on citizens to finance their punishment activities, however, we find a Goldilocks effect. Citizen cooperation is maximized when legal rules evolve at a critical evolutionary rate that is slow enough to allow citizens to adapt, but fast enough to enable States to quickly respond to outbreaks of citizen lawlessness.