For more than twenty years, the question of defining science limits in situation of uncertainty is a major concern for the philosophies of sciences. If Ulrich Beck’s major work laid foundations for sociology of science focused on reflexivity and environmental risks, other like Bruno Latour choose to pay attention to “black boxes” and their socials consequences. But, in an expected “sustainable” society, science shall be analyzed as a complex object at the crossroad of economic, environmental, social and political issues. For example, the unfinished process of defining “risk” attests the complexity for sciences to establish a control over nature’s uncertainty. In fact, the difficulty to find a socially, scientifically and politically accepted definition of risk slowly changed the scientific discussion in a struggle for controlling this concept at the cornerstone of every environmental policy in a postmodern society. From risk assessment to risk management, this work analyzes the transformations and evolutions of the “risk” concept. It questions the uncertainty of nature, human actions and their consequences, science and its limits. The main results are drawn from the study of a public deliberation process within the European public space: the European Commission’s Thematic strategy on the sustainable use of pesticides. It follows actors who tried to control the whole procedure by describing their discursive strategies and the discursive formations they constructed. These actors – institutional or not –control, transform and alter “risk” by creating new semantic concordances and other definitions. In these attempts to control the concept and to legitimize one definition instead of another, all stakeholders constructed new structures and new objects that needed to be analyzed. The main problem of this study therefore lies in the observation of a concept circulations and transformations, in a specific organizational and communication context. Focusing on European Commission’s sustainable development policies allows to “re-contextualize” sociological and historical researches on the structure and controls of the public space, from the Ancient Greek polis to the European public space in Habermas’ sens. This research project is as well an epistemological investigation of environmental studies and a sociological analysis of the construction of an environmental problem. Hence, this paper aims to reports the analysis results of European Commission’s institutionalization strategies and control procedures. In addition, it conducts a qualitative discourse analysis of more than 150 stakeholders’ contributions to the debate. The findings of this study are interpreted in order to propose a methodological approach of complex legislative processes regarding sustainable development and environmental regulations. Nevertheless, as the analysis shows success and failures of science’s control, this research wants to be an opportunity for a theoretical discussion about the patterns of discourse control in public space and risk studies. If the society and the social science fails to understand the definition process of risk, what is now a cornerstone of the public debate may become the sustainable development stumbling stone.