Despite the guidelines provided in the Constitution, many fundamental constitutional issues remain open to debate after two centuries. One of the thorniest centers on the division of authority. Who is actually mandated by the U.S. Constitution to carry out the duties it imposes? Alexander and Horton address this question by developing several models of constitutional interpretation and applying them to "state action, "under color of law," and other complex doctrines in constitutional jurisprudence that have been created to deal with problems of distinguishing "unconstitutional" from "merely illegal" authority. Presenting three basic analytical models--"legalist," "naturalist," and "governmental"--together with several possible permutations, the authors clarify the assumptions underlying these current doctrinal tangles and illuminate many conflicts and inner inconsistencies of modern constitutional law. They examine the implications of each model in terms of its application to relevant court precedent and the way it would deal with specific constitutional provisions such as the Thirteenth and Fourth Amendments and the Commerce Clause. The authors conclude that only two of the possible models can be considered to be principled.