The article underlines applicability of relationistic and systemic approaches to a phenomenon of the power and subsequent power relations. Relationists consider power and subsequent power relations as a possibility for an individual or group to change the behavior of another individual or group. In the systemic approach power is defined as a specific impersonal quality of political system, as an internal functional, not joined by an individual or group of individuals. The article develops some points on advantages of the systemic approach for an understanding of power relations in the Medieval societies as a public process. Key elements of the conceptual scheme are realized within a context, which determined major trends in development of an idea of absolute royal power in the Western European monarchies. Suggesting that medieval concept of the royal prerogatives was influenced by theological and legal (almost canon law) discourses, the author demonstrates how they were finely unified in the 14th century intellectual controversies and in what way they became instrumental for Baldus de Ubaldis’s political thought. New preferences were based on a strong distinction of an absolute and ordained power: supreme secular authorities, while functioned, perceived their unlimited prerogatives as a perspective potential but emphasized a constructiveness of applicability of their limited credentials.