In the past two decades international anthropological critique has focused on issues such as: the discipline's colonial roots, how the concept of culture is embedded in the colonial milieu, the relationship between the texts of academic anthropologists and those produced by the "men on the spot", and finally how administrators/ethnographers contributed to shape local ethnic identities. The essay is an attempt to apply some of these suggestions to Italian colonialism. It explores the case of the colonial officer Alberto Pollera (1873-1939) who published a consistent number of ethnographic essays and acted as colonial administrator and judge "vis-à-vis" the local populations. The essay focuses on the early scripts of Pollera on customary norms among two Eritrean groups. It shows how his ethnographic knowledge influenced both the representations of local groups and his administrative policy which, in turn, contributed to the creation of fixed and separate ethnic identities. It also shows how his historical interpretation allows for an embryonic form of relativism and functionalism, which is paralleled by a creed in the evolutionist paradigm.