In Brazil, when talking about Indigenous Lands ("Terras Indígenas" or TIs), one has to bear in mind, in the first place, the definition of it and a few juridical concepts established by the 1988 Federal Constitution, and also in specific legislation, especially in the Estatuto do Índio - Statute of the Indian - (Law 6,001/73), which is currently under revision by the National Congress.
The 1988 Constitution consecrated the principle that the Indians are the first and natural owners of Brazilian lands. That is the primary source of their right, and one that precedes any other right. In consequence, constitutionally the right of the Indians over a given land does not depend of formal recognition.
The definition of lands traditionally occupied by the Indians is found on the first paragraph of Article 231 of the Federal Constitution: they are those lands "inhabited by them permanently, those used for their productive activities, those indispensable to the preservation of the environmental resources necessary for their well-being and those necessary for their physical and cultural reproduction, in accordance to their habits, customs and traditions".
Article 20 establishes that these lands are the Union’s property, and that it is recognized to the Indians the permanent possession and the exclusive usufruct of the riches of the soil, the rivers and the lakes existing in them.
However, the Constitution also requires the Public Power to promote such recognition. When an Indian community occupies a given area as described on Article 231, the State has to delimit it and promote the physical demarcation of its limits. The Constitution itself established a deadline for the demarcation of all Indigenous Lands (TIs) in Brazil: October 5, 1993. The deadline, however, was not met, and today TIs can still be found in various juridical statuses (demarcation).
A good many Indigenous Lands in Brazil are subjected to invasions by mining enterprises, fishermen, hunters, timber companies and ‘posseiros’ (illegal homesteaders). Other are crossed by highways, railroads and transmission lines, or have been partially flooded by lakes formed by hydroelectric plants. Frequently the Indians end up paying the perverse consequences of things that happen outside their lands, in neighboring areas: pollution of rivers by pesticides, deforestation and so on.