This paper explores use of the Delphi technique on regulatory impact assessment (RIA) in order to select criteria as well as to analyze the non-neutrality of stakeholders in the Portuguese case study. Although the decision-making process has been supporting a different prescriptive approach, there is no neutral decision, which can reflect on the (in)efficiency of the government's action. To cope with imperfect knowledge, we have built the link between the objectives from Law no. 194/2009, which determines the regulatory framework in the Portuguese water sector and its potential criteria. Moreover, the elicitation weights for each criterion previously selected were framed in an innovative way, under a different perspective, either customers, municipalities or concessionaires. Evidence advises that there are relevant myopic, omission, splitting, and insensitivity biases for decision analysis, because of the distortion of input. Thus, the Delphi technique enables the decision makers to obtain reliable information before taking a decision. The results in terms of a different perspective for each criterion enable us not only to identify the non-neutrality of decision analysis, but also to (re)think the stakeholder's participation into the context of the Law referred to. Finally, this approach could consolidate our understanding concerning the potentialities of the Delphi technique in RIA, especially in policies with several objectives.