A theory of legal development, derived from cognitive developmental theory, is explicated using U.S. kindergarten to college and cross-national preadolescent data. Paralleling evidence on universal moral levels, the development of individual orientations vis-à-vis legal or rule systems reveals consistent movement from a preconventional law-obeying, to a conventional law-maintaining, to a postconventional lawmaking perspective. In both the U.S. and cross-national samples, “law and order” conventional reasoning is modal reflecting that socialization experiences can accelerate, retard, or crystallize the growth of legal values and roles. Implications of the theory and findings are discussed for legal socialization.