In questa tesis si studia il principio di separazione dei poteri nei suoi origini e sua evoluzione storico-politica. In seguito si analizza sua articolazione nei diversi paesi europei finendo con la sua strutturazione nell'Unione Europea, concludendo con una proposta di nuova struttururazione.

The aim of this doctoral thesis is to study the historical and doctrinal evolution of the separation of powers, firstly as a political principle, later as a political praxis in its most perfect model, the United States of America. In a second phase its articulation in several European states is studied, attending to the form of the states and to the degree of their politic and administrative decentralization. Finally, this thesis studies its structure in the European Union, concluding with a political and institutional proposal of reform.