In a context where civil societies build different ways of interacting with the State, informal arrangements contain important strategies for the process of articulating social organizations and movements, especially in microterritories. Nevertheless, the issue of informality exposes repertoires that do not pass the rules by which institutions operate and, in most cases, are excluded from the analysis because they are considered clientelist strategies and identified as not very transparent and democratic. Given this context, the present study analyzes, in an approach on state permeability (MARQUES, 1999) and intervening mechanisms in socio-state interaction (LAVALLE; CARLOS; DOWBOR; SZWAKO, 2018), the trajectory of the Federation of Bacamarteiros of Pernambuco (Febape). Through the application of semi-structured interviews with leaders, ex-leaders and federated members, we seek to understand how the informal dimension permeates the processes of interaction between the organization and the State institutions and to what extent this dimension is able to influence public policy formulation processes. Furthermore, based on a theoretical effort that combines assumptions of historical institutionalism and the theory of new social movements, we sought to develop a frame of reference on the intervening mechanisms in the interactions between State and society and, finally, to identify the network of actors constituted by the federation in the process of building legitimacy inside and outside the institutional framework. The results of the study demonstrate that Febape's trajectory is marked by the constitution of an informal arrangement based on personal relationships between leaders and bureaucrats, based on the sharing of values and identity traits. In this sense, it was possible to observe that these ties contributed to make the State permeable to external interests, enabling the construction of “access points” to institutions through the figure of the “internal collaborating agent” and allowing a civil society organization the possibility of include your demand on the institutional agenda and influence the State from the inside.