THE PRESENCE OF CUSTOMS IN BRAZILIAN JURISPRUDENCE: A WEIGHTED ANALYSIS OF THE IMPORTANCE OF SUCH LEGAL INSTITUTES IN THE PRODUCTION, SHAPING, AND ENFORCEMENT OF SUPERIOR COURTS’ DECISIONS

Abstract

This article examines the presence and applicability of customs as a source of law in the Brazilian legal system, investigating the following research problem: to what extent do legal customs – understood as repeated social practice accompanied by the conviction of obligatoriness (opinio iuris) – influence the reasoning behind decisions handed down by Brazil’s Superior Courts? The central hypothesis holds that, notwithstanding the primacy of written law in the Romano-Germanic system, customs play a relevant subsidiary normative role, filling legal gaps and guiding judicial hermeneutics, as authorized by Article 4 of the Brazilian Law of Introduction to Legal Norms (LINDB). This is a bibliographic and documentary study, with a qualitative approach and deductive method, including qualitative case-law analysis of judgments from the Superior Court of Justice (STJ) and the Federal Supreme Court (STF). The theoretical framework draws on classic and contemporary authors such as Miguel Reale, Maria Helena Diniz, Norberto Bobbio, Hans Kelsen and Valerio de Oliveira Mazzuoli. The results partially confirm the hypothesis: customary law is recognized by the Brazilian legal system as a subsidiary source, but its autonomous normative efficacy is constrained by the supremacy of positive law, especially in criminal law, where the principle of strict legality prevails. The study further shows that custom performs distinct roles depending on the normative plane at stake: in domestic law it is a subsidiary source, contained by constitutional limits on its positivization; in Public International Law, by contrast, it is a primary and autonomous source, although subject to relativization by the constitutional principles governing Brazil’s international relations.