While Common law is generally uncodified and is largely based on precedent (i.e. judicial decisions that have already been made in similar cases), Civil law is codified. Countries with civil law systems have comprehensive, continuously updated legal codes that specify all matters capable of being brought before a court, the applicable procedure, and the appropriate punishment for each offense.
In a Civil law system, the judge’s role is to establish the facts of the case and to apply the provisions of the applicable code. The judge’s decision is consequently less crucial in shaping civil law than the decisions of legislators and legal scholars who draft and interpret the codes.
By contrast Common law functions as an adversarial system, a contest between two opposing parties before a judge who moderates. A jury of ordinary people without legal training decides on the facts of the case. The judge then determines the appropriate sentence based on the jury’s verdict. As a result, judges have an enormous role in shaping American and British law.
(adapted from https://www.law.berkeley.edu/library/robbins/commonLawCivilLawTraditions.html)
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