Among the pre-conditions for establishing a colonial order must have been monopolistic control of physical force and penal setting; but colonial regime needed to activate more subtle uses of customary laws. The article deals with technicians and scholars-administrators in charge in Ethiopia after the fascist military conquest of 1936. The private archive of a colonial officer, G. Ellero, offers a fragmented collection of data on a single juridical custom named "awciacc". The northern regions of Tigray offered a coexistence of multiple histories and challenged the colonial understanding. The social order was arena of debate, customary law an interactive and processual construction within the colonial context, the judicial setting part of the process of coercion and the coming together of a set of differents assumptions and interests. The attempt to legitimate the new regime emphasized the critical role of chiefs and interpreters, the multiple and conflicting discourses and strategies giving meaning to single customs. Constructing a customary law was both a process of colonial imagination and an instrument of power.