This paper is an example of the application of social design thinking in the Hellenic Council of State, the Supreme Administrative Court. It refers to the Court’s capacity building as a control system to cope with environmental protection issues. The idea of environmental protection, along with that of development, was recognized for the first time in 1972 at the Stockholm Conference (United Nations 1972). As environmental problems aggravated to the point that they threatened man’s survival on earth (global warming, deforestation, loss of biodiversity, etc.), in 1992, the Rio Declaration proclaimed the end of one-dimensional economic development and replaced it with “Sustainable Development.” The Declaration was accompanied by Agenda 21, Humanity’s Strategic Plan for the twenty-first century (United Nations 1992). At the Rio Conference, Greece announced the formation of a special section within the Council of State with jurisdiction over environmental matters. This constituted the 140country’s main contribution to the effective protection of the environment. By the year 1996, a pioneering jurisprudence of that section emerged covering almost all aspects of the relation between man and the environment. The paper refers to the main characteristics of the design of that jurisprudence and its relation to the value system of classical Greece, and it provides a glance into the black box of a judicial process. The process includes (a) the depiction of sustainability as a system of interdependent values. This system provided the tool for value analysis (systemic axiology) in the decision-making process; (b) a shift in legal methodology from mere rule interpretation to problem solving, thus introducing effectiveness in a process which hitherto produced “paper law”; and (c) creation of substantial general principles of the Law of Sustainable Development from the whole to its parts and application of these principles, which restore unity of law and justice. Plato’s Republic is taken as the example of a “just” society incorporating Greek values and is compared with the values of the sustainable society of the twenty-first century.