Custom’s Pervasive Role in Law and the Boundaries of Positivism

Custom is law’s foundation, modulator, and occasional antithesis. This Article explores that relationship, starting with varying insights from some of the few legal philosophers who have examined the custom/law dynamic. The heart of this Article provides examples showing custom’s many influences on the law, set in five functional areas: origin, application, interstitial, rule-source, and oppositional. Although the custom/law interplay spans human behavior, these examples come from law practice where custom is exposed.

Many are routine, some are significant, and all show our reliance on behaviors and norms that are not positive law. The conclusion addresses but does not resolve some of the many questions inherent in this complexity. In a positive law democracy, should a court ever be obligated to rely on a free-standing custom in the absence of positive law? What if a long-standing custom is contrary to a desuetudinal statute or precedent?

To the extent courts ought to heed custom in any setting, how is it assessed? The topic is vast and this Article’s point necessarily modest, merely illustrating the phenomenon of custom’s pervasive role in law.