One way of doing so is to more precisely define the contours of states’ obligations towards foreign investors and investments, in an attempt to eliminate the likelihood of successful challenges to non-discriminatory public welfare measures. More precise norms place greater constraints on the decision-making criteria employed by adjudicators, fettering their discretion to make evaluative judgments. Treaty parties may adopt more precise language to provide guidance or to exert control over adjudi- cators in light of previous decisions that are regarded as erroneous, in light of concerns about adjudicator incompetence or to constrain subjective value choices.