Global trade and marketing are subject to laws, rules, and regulations formulated by diverse legal systems. There are five different legal systems in the world. No one system dominates the world’s legal landscape, but Common, Civil, and Muslim law are dominant. Only about 30 percent of the world’s gross domestic product is generated in countries governed by civil and common law systems. Civil law systems are based mainly on Roman law heritage and are found in Europe, Asia, Central and South America. They consist of a comprehensive system of rules, or legislation, usually codified, that are applied and interpreted by judges. Common law, adopted in North America, is based on English custom, where court adjudications are the primary source of law, although governments pass statutes and legislation that are only seen as incursions into the common law and thus interpreted narrowly. Each case that raises new issues is considered on its own merits, and then becomes a precedent for future decisions on that same issue. Exceptions include the State of Louisiana in the United States, whose legal system is based on the Napoleonic Code, and Quebec, which adheres to civil law.