This work aims to draw attention to the importance of the involvement of citizens in decision-making related to the environment, through access to public spaces for discussion, deliberating for understanding and seeking thus the achievement of Democratic State of Law. Such participatory State has among its objectives to build a fair, free and solidary society, both in economic, social and environmental perspectives, aiming at the deficitary representation that has promoted social and environmental injustices, which can raise the possibility to experience a Socionenviromental State of Law. From Habermas theory, it is shown that the decisions that have the environment - fundamental diffuse and transindividual right - as the object, will be more legitimate if individuals could effectively participate in them, not only as spectators but also as protagonists. These actors should be aware to the environmental sustainability and balance when suffering tensions due to the need for economic development and should prevent particularistic positions to gain the status of universals. The concrete unfolding of this participation in socioenvironmental issues takes place currently through public hearings in the environmental licensing, in previous public consultations for the creation and expansion of conservation units, and in public hearings held in the judgments of the Supreme Court that relate to the environment - despite the existing difficulties regarding the effective citizen interaction through participatory instruments under the Brazilian legal system - and so it figures as a picture of popular participation in environmental protection in the framework of deliberative democracy, according to Habermas theory.