Lasser’s study Judicial Deliberations offers an interesting analysis of judicial discourse and legal argumentation. For theorists of legal argumentation Judicial Deliberations is an interesting project, because of its theoretical perspective, its methods and its results. In the past thirty years the study of legal argumentation has increasingly become an important field of interest. In this paper I discuss some of Lasser’s conceptual and empirical contributions to this theory of legal interpretation and argumentation. I will do this by exploring Lasser’s analysis of the difference between interpretative justification in Common Law and Civil Law countries, focusing on the difference between formal and substantial interpretative argumentation in legal decisions. In short, I will discuss Lasser’s lack of conceptualization of the distinction between formal and substantial interpretative argumentation, his methodological choices and the generalization of his empirical findings.