Customary Law

Custom is a practice or established habit of behavior, particularly in the interaction among people involving issues that could have legal ramifications. Collectively, common communal or cultural practices can evolve into a regime of legal norms considered customary law. Legal regimes developed, particularly in Europe, as a culmination of precedents that only became established after a long duration of time. Customary law is practiced in many contexts -- by secular governments, religious sects and even sports. In Judaism and Islam, established custom can be considered a precedent to resolve a dispute brought before religious jurists who might otherwise find no precedent in the religion's holy texts to decide a case. Additionally, within Judaism, the habituation of a behavior can become legally binding on its practitioner, arguably without intention, creating an expectation and obligation that imbues custom with uncharacteristic strength versus legislated or so-called revealed law.

Custom is considered the origin of several contemporary legal structures. English common law has its origins in accepted communal practice, but it also has incorporated changes in society's customs into its legislation and judicial decisions. While English common law is referenced by many legal scholars, the same process is apparent in all cultures. Many states, governing diverse populations that often still owe allegiance to a tribal structure above the nation-state, negotiate with those tribal or traditional leadership structures that offer varying degrees of autonomy where established or developing local custom can become the normative law by which people are judged, rather than adhering to the courts of the nation-state. This has upset many theorists who believe states will not achieve stability by allowing such leniency. However, many point to federal systems where states, provinces or regions are deputized to govern their own jurisdictions even to the point they may enforce laws that are different from other regions of the greater state. Thus, this analogy has been extended to autonomous customary legal systems, often in apparently underdeveloped countries.

International law, given its still developing conventions and agreements, has relied primarily on custom to adjudicate issues among countries. However, the effect of the use of custom and extensive use of analogy has arguably been damaged by the lack of an international policing mechanism that can apprehend suspects, namely world leaders. Additionally, the advantage of certain states that can align with others of similar ethnic and cultural heritage has given disproportionate advantage to seek indictments and charges to countries who do not face enough pressure themselves. Stated plainly by Michael Byers, "few international lawyers have considered directly the role played by power in the process of customary international law."

Article 38 in the Statute of the International Court of Justice maintains "a general practice accepted as law" as the definition of custom, inviting severe critique on a constitutional level. The imposition of established custom could invalidate the evolution of new customs and give arbitrary force to practices that, at the time of their enforcement, would be considered outdated. This problem has also been identified in religious context, where in Judaism an older generation's refrain from a certain practice could be entirely abrogated by a younger one: An example currently plaguing the community is the use or non-use of electricity on the Sabbath. Arguably, the younger generation should be beholden to the restrictions of the older, but imposing it is difficult since understandings of what electricity constitutes have changed and would have had an impact on the previous generation's decision whether or not to refrain from its use. However, there are other sources that consider custom still to have force even if practitioners only took on the habit out of the belief the custom was, in fact, a law. Arising from this, mistakenly or not, is a sense of obligation known as opinio juris in legal circles.

This has been a matter of dispute in religious, secular and civil legal settings where the practices of one party may be culturally or generationally distinct. Many would also consider custom coming out of mistaken belief to be illegitimate; someone who might be enlightened to the fact there is no decreed or legislated obligation might be happy and see it appropriate to do away with the custom. However, jurists in many different settings might consider the sense of obligation more authoritative than the conscious acceptance of a customary practice to have force.

Customary Law: Selected full-text books and articles

The Nature of African Customary Law By T. Olawale Elias Manchester University Press, 1956
The Coutumes de Beauvaisis of Philippe de Beaumanoir By Philippe de Remi Beaumanoir; F. R. P. Akehurst University of Pennsylvania Press, 1992
Law and Revolution: The Formation of the Western Legal Tradition By Harold J. Berman Harvard University Press, 1983
Librarian's tip: Chap. 1 "The Background of the Western Legal Tradition: The Folklaw"
Medieval Society and the Manor Court By Zvi Razi; Richard Smith Clarendon Press, 1996
Librarian's tip: Chap. 3 "What Did English Villagers Mean by 'Customary Law'?"
Custom in the Courtroom, Law in the Village: Legal Transformations in Papua New Guinea By Demian, Melissa Journal of the Royal Anthropological Institute, Vol. 9, No. 1, March 2003
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
Yoruba Land Law By P. C. Lloyd Oxford University Press, 1962
Librarian's tip: Chap. 2 "Customary Law"
Kingdoms and Communities in Western Europe, 900-1300 By Susan Reynolds Oxford University, 1997 (2nd edition)
Librarian's tip: "Customary Law" begins on p. 13
Studies in International Space Law By Bin Cheng Clarendon Press, 1997
Librarian's tip: Chap. 7 "United Nations Resolutions On Outer Space: 'Instant' International Customary Law?"
International Law and the Use of Force by States By Ian Brownlie Clarendon Press, 1963
Librarian's tip: Chap. 2 "The Customary Law of the Period 1815-1914: Some New Developments: Arbitration and Treaties for Pacific Settlement"
International Law concerning Child Civilians in Armed Conflict By Jenny Kuper Clarendon Press, 1997
Librarian's tip: Chap. 5 "Customary Law"
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