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Why do common-law countries rely more heavily on earlier judicial decisions than civil-law countries?

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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.

Common-law countries rely more heavily on earlier judicial decisions because of the principle of stare decisis—Latin for "let the decision stand"—which mandates that courts follow established precedents to ensure the law remains uniform, predictable, and fair. In these systems, judicial decisions are considered a primary source of law, and judges often create legal rules where no statutory foundation exists.123

In contrast, civil-law systems are based on comprehensive legislative codes that aim to provide ready-made answers for legal issues. Theoretically, civil-law judges do not create law but merely apply the statutes enacted by the legislature. While civil-law judges do interpret vague provisions and fill legislative gaps, these decisions are not formally binding as precedents.3

Ultimately, the reliance on precedent in common-law systems reflects a fundamental commitment to the ethical principle that similar cases should be treated similarly, fostering consistency and justice across the legal system.3