In common law legal systems, the law is created and/or refined by judges: a decision in the case currently pending depends on decisions in previous cases and affects the law to be applied in future cases. When there is no authoritative statement of the law, common law judges have the authority and duty to "make" law by creating precedent.[1] 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 (this principle is known as stare decisis). If, however, the court finds that the current dispute is fundamentally distinct from all previous cases, it will decide as a "matter of first impression." Thereafter, the new decision becomes precedent, and will bind future courts under the principle of stare decisis.
In practice, common law systems are considerably more complicated than the "ideal" system described above. The decisions of a court are binding only in a particular jurisdiction, and even within a given jurisdiction, some courts have more power than others. For example, in most jurisdictions, decisions by appellate courts are binding on lower courts in the same jurisdiction and on future decisions of the same appellate court, but decisions of non-appellate courts are only non-binding persuasive authority. Interactions between constitutional law, common law, statutory law and regulatory law also give rise to considerable complexity. However stare decisis, the principle that similar cases should be decided according to similar rules, lies at the heart of all common law systems.
Common law legal systems are in widespread use, particularly in those nations which trace their legal heritage to Britain, including the United Kingdom, the United States, most of Canada, and other former colonies of the British Empire.
