This dissertation aims at the interdisciplinary study of legal rules as applied by legal authorities. The research is divided in two parts. Part I’s objective is to understand the psychological relationship between decision-making authorities and rules through a sociopsychological construct dubbed attitude towards rules, as well as its possible relations with the process of creating exceptions to rules in recalcitrant experiences, with personality traits from the Big Five Factors model, and with sociodemographic variables. After following the procedure for constructing the psychological tests, we proceeded to search for evidence of validity of the Attitude Towards Rules Scale (ATRS) containing 29 items. The complete instrument containing sociodemographic items, the ATRS, the Brazilian Short Form Scale of Descriptors of the Five Personality Factors, and hypothetical cases to be judged by the participants, was submitted to a diverse sample of 347 lawyers from Justice System or Law School graduates. The results provide evidence for the internal validity of the sociopsychological construct attitude towards rules, measured by the ATRS with 12 items (Cronbach s alpha = 0.89). Evidence for external validity was also found in correlations with the personality trait openness to experience, with various emotions and self-perceived feelings, with sociodemographic variables (e.g., place of residence and domain of professional activity of the subject) as well as with the averages for the subjects’ judgments in items 2 and 3 of the hypothetical cases presented, allowing for a justified interpretative statement such that the psychological relationship between decision-making authorities and rules could be conceived as an attitude. Attitude towards rules also correlated in the expected way with the responses in concrete cases, except in one case, in which the construct seems to have surpassed its expected conceptual boundaries. Part II was motivated by this finding and aimed to seek a theoretical explanation, in addition to organizing the theoretical and empirical findings into a comprehensive model of legal decision-making. To this end, several topics related to legal exceptions were examined: its concept, the difference between predicative exceptions and the process of excepting norms, the elements of this process, with emphasis on normality judgments, and the possible results (meaning change vs. defeasibility). From these distinctions, it was hypothesized that the empirical finding that motivated the continuation of the research is partially explained by normality judgments on the functioning of the Law, which may initiate the process of excepting norms. Finally, the theoretical and empirical collection is organized into a comprehensive model of legal decision-making, which encompasses both normality and abnormality, routine cases and unusual cases, easy cases, and hard cases. The Conclusion organizes the central ideas of this dissertation, summarizes its main findings and reviews the main implications for Psychology, for Legal Theory, and for Industrial and Organizational Psychology.