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Why is Louisiana different from other U.S. states in its use of civil law?

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Mosaic portrait of Emperor Justinian I with a jeweled crown and halo, from the 6th-century Basilica of San Vitale in Ravenna, Italy. — Civil law Justinian I, detail of a 6th-century mosaic at the Church of San Vitale, Ravenna, Italy.

Louisiana’s legal system is unique among the 50 U.S. states because it is based on civil law rather than the common law tradition followed by the rest of the country.12

This distinction stems from Louisiana’s colonial history. The state’s legal framework draws from a heritage that adopted codes based on the Napoleonic Code of France and was further influenced by Spanish laws, both of which share a common foundation in Roman law.1

In this system, the law is enacted as a comprehensive set of written codes consisting of broad principles. Consequently, the role of the judiciary is limited to applying these established laws to specific facts, and courts are not bound by previous judicial decisions (precedent) in the same manner as common-law jurisdictions. While other states have adopted various statutes, Louisiana remains the only U.S. state that maintains a code in the true civil-law sense, where the code serves as the authoritative starting point for legal reasoning.12