In this discussion, the author distinguishes the authoritative source of law from the substantial source of law. The authoritative source of law is the political body that confers authority on the decision maker to select and interpret the rule. By doing this that body politic creates the authority that gives the rule status as a rule of law in the forum of decision. The substantial source of a legal rule is that body of law in which the rule's original policy bases and the verbal form that describes the effect to be given to that policy are found. The substantial source of the rule is not necessarily the same political body or unit that is its authoritative source. Both these sources are distinguished from the energizing forces that stimulate the legal dynamic. Those forces are the combined felt community needs that give life to every rule of law and justify its continued use as a guide to authoritative decision making.
Harold G. Maier,
The Authoritative Sources of Customary International Law in the United States,
Mich. J. Int'l L.
Available at: https://repository.law.umich.edu/mjil/vol10/iss2/6