Reviewed by: Custom as a Source of Law Sean O. Sheridan T.O.R. Custom as a Source of Law by David J. Bederman. New York: Cambridge University Press, 2010. Canons 23 through 28 of the 1983 Code of Canon Law provide the ius vigens on the issue of custom as a source of law in the Church. Specifically, canon 23 states: "Only that custom introduced by a community of the faithful and approved by the legislator according to the norm of the following canons has the force of law." The use of custom as a basis for law has a long standing tradition in the Church, but also in the laws of civil society. In his book entitled Custom as a Source of Law, Bederman traces the historical development and the significance of custom as a source of law in an effort to identify its role in the modern legal system. Bederman's book, based on a series of lectures that he presented in a course for law students at Emory University School of Law, is divided into three major parts. Part One, "Customary Law in Perspective," focuses on the historical development of custom as a source of law from an anthropological perspective (3-1), a cultural perspective (16-26), an historical perspective (27-41), and an economic, sociobiological and psychological perspective (42-53). Part Two, "Custom in Domestic Legal Systems," addresses the use of custom as a source of law in specific areas: family law (57-67), property (68-79), contracts (80-90), torts (91-100) and constitutional law (101-113). Lastly, Part Three, "Custom in International Law," considers the issue from the perspectives of private international law (117-134) and public international law (135-167). Although Bederman does not address the Church's current understanding of custom as a source of law, he does consider briefly the role of custom in the ius commune (22-25), which would be of particular interest to medieval historians. He recognizes the development of custom from Roman law through its consideration by the medieval canonist Gratian. He suggests that, in some respect for Gratian, custom as a source of law was an attempt "to suppress dangerous or irrational customs" (23-24) but also an extension and enrichment of the classical Roman Law treatment of the question (24). For the most part, although the other topics in the book appear to be well researched and well written, they would in all likelihood be most interesting to historians or civil law academicians, rather than to canonists or even civil law practitioners. Certainly, analogies to the principles of canon law might be drawn from Bederman's treatment of issues such as family [End Page 284] law (57-67), which could, for example, be incorporated into a decision on the question of the nullity of a marriage. Similar consideration might be made for questions on temporal goods with regard to Bederman's treatment of custom as a source of law for property issues (68-79) or the interpretation of contracts (80-90). The same could also be said for civil lawyers in private practice who might make use of this information. Perhaps Bederman himself best acknowledges the challenge presented by the issue of custom as a source of law through his conclusion that "as tempting as it would be to propose here a unified theory for custom's formation, such, alas, is impossible." (171). Nonetheless, Bederman should be commended for his contribution to the discussion. Sean O. Sheridan T.O.R. The Catholic University of America School of Canon Law Washington DC Copyright © 2012 The Catholic University of America Press