In Mexico the official boundaries defining archaeological zones become critical elements in protecting the remains of pre-Columbian cultures. "Boundary-setting…is a process by which one or more pieces of evidence of pre-Columbian cultures are protected, and is carried out through a topographic survey which establishes boundary markers in the field and locates them on a map of the zone with landmarks of key relevance " (Sanchez Caero 1995: 187). These, under the authority granted by the Federal Law on Archaeological, Artistic, and Historic Monuments in its articles 38 and 39, chapter IV (INAH 1980), are decisions of the National Institute of Anthropology and History, whose archaeological experts carry out field surveys and provide the technical boundaries of the site in question.
By establishing the perimeter of a site one automatically defines a geographic space containing the remains from one or more pre-Columbian cultures, and this space then may be considered for official proclamation as an Archaeological Monument Zone via a presidential decree, under federal jurisdiction, in accordance with article 37, chapter IV, of the law cited above. To achieve a presidential declaration requires the preparation of a substantial technical file which presents the arguments for the case. In turn this means carrying out the fieldwork necessary to identify the boundaries of the site and to carry out the technical topographic work. This phase of the process is usually carried out by one or more archaeologists familiar with the site and/or the region, and by special surveyors from INAH's Sub-directorate of the Public Registry of Archaeological Monuments and Zones (SRPMZA).It also requires calculation of the number of hectares affected by the survey, and a scientific study which explains the cultural importance of the site.
With regard to the technical and scientific criteria used to suggest the boundaries of the archaeological zones, to date and despite ample experience in the subject, the SRPMZA of INAH has not prepared official guidelines to establish boundaries (manuals summarizing procedures, general guidelines and exceptions, or other documentation). Each site is considered as a unique case and its concerns are dealt with on a individual basis. It is in specific materials in the technical files which normally accompany the official boundary-setting process that the technical staff who are normally a part of this process take advantage of circumstances to suggest reasons and criteria for placement of of the boundary markers establishing protection for the area.
In the mid-1990s the union to which the research staff of INAH belong sought to articulate staff perspectives with regard to protection of cultural heritage. A number of worthwhile points came out, including the importance of realistic and readily-understood criteria for boundary-setting, sensitivity to the breadth of topics which might form part of the technical file, e.g., studies of the natural environment or of relevant human settlements, and the necessity to revisit critical factors in international documents such as the Charter of Athens and the Guidelines of Quito (Sanchez 1995: 192). The Guidelines support the idea that boundaries should be based on a system of zones which recognize:
1. A Rigorous Protection Zone, corresponding to the highest concentration of structural or environmental elements;
an Intermediate Protection Zone, with a greater degree of tolerance; and
2. an Urban Landscape Protection Zone, facilitating integration of the same with the larger landscape (Sanchez 1995).
He goes on to comment:
Factors meriting consideration in archaeological zone protection include the archaeological remains, the natural environment surrounding the zone, the relationship of modern settlements in historic context, plus resolutions of land tenure and land use, and finally the agreement among archaeologists regarding the parameters to be applied in setting boundaries (Sanchez 1995: 194).
Between 1980 and 1990 there are several examples of attempts to implement these criteria, as in the cases of boundary-setting at Teotihuacan, Cholula, Chichen Itza, and the extensive zone of Puuc in the Yucatan. Nevertheless, in none of these cases was it possible to develop a strong relationship between the planning proposals, the political commitment among all actors necessary for effective regulation, and much less an anthropological study which would have permitted an evaluation with some degree of certainty of potential social problems the process of boundary-setting would face. The result in each one of these cases is that within a few years of boundary-setting protected areas are invaded for housing, by street vendors, for the installation of tourist services, or urban infrastructure, all authorized or tolerated by different local, municipal, state, and even federal agencies.