In this paper, concepts of contractualism, neo-contractualism, categorical imperative, veil of ignorance, human rights, citizenship, and substantive democracy are discussed to analyze the rationale that neo-contractualism theories offer to explain and legitimize the rule of law as a state capable of ensure fundamental human rights and guarantees to citizens. Once the concepts discussed have been applied, the adequacy and capacity of the Brazilian State, according to its form of state and its regime of government, is analyzed to guarantee the social welfare that is proposed in its Basic Charter, trying to evaluate the efficiency of representative and participatory democracy to direct legislative production, the formation of agendas and the management of public resources to meet the urgent and emerging needs of the population.