In protected areas the relationship of people with their environment is defined by the stated objectives of ensuring a form of cohabitation designed to achieve “harmonization” between nature and society. Juridical regulations, however, result in involving a greater number of managers from outside the areas considered than of stakeholders living there. The amendment of French national parks legislation raises the question of the nature of law in protected areas. Could a law that is negotiated rather than imposed be envisaged? The question may legitimately be raised for the French Guiana Amazonian Park in which several indigenous and local communities displaying a marked socio-cultural diversity are included in the “adhesion area”. The law is faced here with another law born out of the practice of endogenous groups. This situation raises questions about establishing a link between the two legal systems (positive law and endogenous law). We start from the assumption of an integrating process of overlapping regulations, i.e. those from the “bottom” and those from the “top” through negotiation. The notion of “negotiated law”, which in the present case is to be forged for the French Guiana Amazonian Park, may be defined and justified by three considerations, taking the Amerindian Wayana community as an example: a) introduction of a law faced with socio-cultural legitimacy; b) integration of the endogenous dimension in coining the law, and c) negotiation of a formalized relationship between practices, local representations and Republican logic. Negotiation led to defining a negotiated law resulting from a syncretism of “being” and “should be” behavioural models coordinated in an intercultural perspective.