COMMON LAW HAS A DEFINITE PLACE IN OUR LEGAL SYSTEM

When there is no authoritative statement of the law, common law judges have the authority and duty to "make" law by creating precedent. The body of precedent is called "common law" and it binds future decisions. In future cases, when parties disagree on what the law is, an "ideal" common law court looks to past precedential decisions of relevant courts. If a similar dispute has been resolved in the past, the court is bound to follow the reasoning used in the prior decision.

Common law originally developed under the inquisitorial system in England during the 12th and 13th centuries, as the collective judicial decisions that were based in tradition, custom and precedent.
Before the Norman Conquest in 1066, justice was administered primarily by county courts, presided over by the diocesan bishop and the sheriff, exercising both ecclesiastical and civil jurisdiction. Trial by jury started in these courts.

There was a large role for unwritten local customs and enforcement could often be arbitrary For example, in England and in most states of the United States, the basic laws of contracts, torts and property do not exist in statute, but only in common law. So that the current legal boundaries of the Constitutional text can only be determined by consulting the common law.

Following the American Revolution, one of the first legislative acts undertaken by each of the newly independent states was to adopt "reception statutes" that gave legal effect to the existing body of English Common Law. Some states enacted reception statutes as legislative statutes, while other states used the English common law through provisions of the state's constitution.

The United States federal government (as opposed to the states) has a variant on a common law system. United States federal courts only act as interpreters of statutes and the constitution, but, unlike state courts, do not act as an independent source of common law. Before 1938, the federal courts, like almost all other common law courts, decided the law on any issue where the relevant legislature (either the U.S. Congress or state legislature, depending on the issue), had not acted, by looking to courts in the same system, that is, other federal courts, even on issues of state law, and even where there was no express grant of authority from Congress or the Constitution.