Courts and scholars refer to the substantive common law applied by tribal courts in the United States using the monolithic term “tribal common law,” but in fact tribal common law can and should be subdivided into two major categories of law – “intertribal common law” and “intratribal common law.” “Intertribal common law” is the common law applied by tribal courts to cases arising out of Anglo-American legal constructs, such as employment contracts or housing leases. “Intratribal common law” is the common law applied by tribal courts to cases arising out of indigenous legal constructs, such as family and inheritance rules or land use rights. Intertribal common law tends to mirror state and federal common law, while intratribal common law derives from the unique and often unwritten tribal customs and traditions. Almost by definition, intratribal common law does not and cannot apply to disputes involving nonmembers.
Matthew L.M. Fletcher, Toward a Theory of Intertribal and Intratribal Common Law, 43 Hous. L. Rev. 701 (2006-2007).