This chapter deals with the problem of legitimacy which, in liberal democracies, results from the pursuit of sustainability or sustainable development as an effort to find a structural solution to the environmental crisis. After giving a rough outline of the political context in which this problem develops, I will discuss the concept of sustainable development as well as some attempts to elaborate it into guidelines for the structural solution or control of environmental problems; I will also give some examples of structural changes in the organization of society which could be the result of the implementation of these guidelines. Thus, the necessity of the legitimacy of a consistent environmental policy, directed at sustainability, becomes clear in a concrete manner. Subsequently, the liberal ideals of political legitimacy and neutrality, and especially Rawls’s idea of an overlapping consensus as a theoretical elaboration of these ideals, will be dealt with. Finally, I will explore whether and to what extent Rawls’s idea is useful, or can be made useful by alteration and supplementation, to the justification of a structural environmental policy which derives from sustainability as a norm. Special attention will be paid to the situation in The Netherlands.