Through administrative documentation, and in the context of the chilenization of the region of Tarapaca and the new demarcation of the border between Chile and Bolivia between the 1890s and the 1920s, this article describes and analyzes the difficulties faced by the aymara peasants to retain their property and the modes of use of their productive resources, the devices and actions they used to defend themselves, and the reactions (some accentuated more by cultural elements, rather than legal ones) of Chilean fiscal officers.