Common Law and Statutory Law

Common Law and Statutory Law

There are two primary sources of laws and legal rules:  legislatures and judges.  When the law has been created by legislators, it is called statutory law.  When it has been created by judges, it is called common law.

Criminal laws are all statutory.  But most of civil law has its origin in common law, albeit modified by various statutes.  The rules of common law are not to be found in codes written by a single authority, but instead in the case law -- that is, the body of decisions made in previous decisions by judges.  The guiding principle of common law is the notion of precedent.  This means that judges are, in general, expected to make rulings that follow the pattern established in previous, similar cases.  When a new case arises whose resolution is not clearly dictated by existing precedents, the judge's decision in the case becomes the precedent for future cases of a similar nature.  In this way, the common law develops over time in response to the cases that appear before the courts. 
Common law is a venerable system with roots that precede the existence of the state.  The Anglo-American common law can be traced back to the local courts of Anglo-Saxon villages, long before there was an English king.  For many centuries, the common law system had authority independent of the king, but eventually the common law system was absorbed into the (previously separate) legal system of the state. 
The United States inherited the common law system of the British, and at some point the U.S. Congress even passed a law that adopted the whole of the British case law as the starting point for American courts.  However, the law has developed differently in each State, so the current precedents may differ from State to State.  Louisiana, which was settled by the French, has a civil code system instead of common law.  Civil code is a system in which all civil law is passed by the legislature, as in France and much of continental Europe.  In the other States, civil law is now a hybrid of common law and civil code.