The Duke Project on Custom and Law

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Exploring the influence of custom on law — past, present, and future

Custom pervades and informs the law:

  • Tort law considers custom in the industry in determining standard of care.

  • Contract law fills in the gaps of commitments based on customary practices.

  • Custom has a significant influence on what is considered “fair use” in intellectual property law.

  • Constitutional law is informed by the customary operations of government.

  • One of the two major forms of international law is customary rather than codified.

  • An understanding of the unwritten institutional customs of legal actors (such as courts and prosecutors’ offices) is often essential to an appreciation of how they operate.

Despite its pervasiveness across almost all areas of law, however, there are enormous gaps in our understanding of what constitutes custom, how it evolves, who gets to decide when norms have become custom, and what its relationship is to more formal sources of law.

This interdisciplinary “conversation” aims to bridge those gaps and advance a scholarly understanding of how custom can support or influence the development of law — through publications, presentations, seminars, workshops, and symposia.