The article advances the hypothesis that the system of potestary coordinates taking shape in thirteenth-century Welsh society reflected the initial stage in the formation of a dominial monarchy. Welsh law demonstrates the incomplete character of this process and, in this respect, points to various forms of fragmentation in power relations. The lawbooks, which reflected both the processes unfolding in thirteenth-century Welsh society and the variability inherent in them, embodied the multilayered and inexplicit characteristics of those processes, giving rise to inconsistencies in the use of rulership terminology. In certain cases, the designations brenhin and arglwydd could be employed synonymously. Their separate — that is, non-overlapping usage marked two distinct profiles of traditional jurisdictional authority within particular Welsh territories. Such a level was understood in legal terms as autonomous, or partially autonomous, but only insofar as the position of the local (peripheral) arglwydd mirrored the prerogatives of his overlord (brenhin/arglwydd).