Common law, also known as case law, is a legal system in which the main body of law is formed by court opinions, which play a defining role in determining how laws are interpreted and applied. In a common law system, previous court decisions are usually respected as precedent and applied to current decisions. Common law is often contrasted with civil law, in which the legal codes and statutes are more meticulous and less open to interpretation and previous court decisions do not necessarily influence the outcome of current cases.
Various systems of law often overlap one another. For example, both common law and civil law rely upon legislators to create the laws and the courts to settle disputes about them. As such, even legal scholars may sometimes disagree as to how a given country's system of law should be categorized. That said, common law is one of the most prevalent legal systems in the world by any measure. Approximately 40 countries and territories use common law, and roughly 60 more use it as part of a mixed legal system in which common law is blended with another form of law—typically civil, religious, or customary law. Common law originated in England in the years following the Norman Conquest of 1066 and spread around the world as England built its empire. Today, common law is used almost exclusively by countries that were once British colonies.
|Country/Territory||Full or Mixed||Country/Territory||Full or Mixed||Country/Territory||Full or Mixed|
|Anguilla||full||Hong Kong||mixed||Papua New Guinea||mixed|
|Antigua and Barbuda||full||India||mixed||Philippines||mixed|
|Australia||full||Ireland||mixed||Saint Helena, Ascension, Tristan da Cunha||full|
|Bahamas||full||Isle of Man||full||Saint Kitts and Nevis||full|
|Bangladesh||mixed||Jamaica||full||Saint Vincent and the Grenadines||full|
|British Virgin Islands||full||Kuwait||mixed||Sint Maarten||mixed|
|Cambodia||mixed||Malawi||mixed||South Georgia and South Sandwich Islands||full|
|Christmas Island||full||Marshall Islands||mixed||Thailand||mixed|
|Cocos (Keeling) Islands||full||Mauritius||mixed||Tokelau||full|
|Coral Sea Islands||full||Montserrat||full||Trinidad and Tobago||full|
|Cyprus||mixed||Myanmar||mixed||Turks and Caicos Islands||full|
|Eswatini||mixed||New Zealand||full||United Kingdom||full|
|Falkland Islands||full||Nigeria||mixed||United States||mixed|
|Fiji||full||Niue||full||US Virgin Islands||full|
|Ghana||mixed||Northern Mariana Islands||full||Wake Island||full|
The only form of law more prevalent than common law is civil law, a system in which the body of law is primarily derived from legal statutes and codes created by legislatures. In civil law, judicial authorities use the civil code to evaluate cases and reach decisions. Civil systems also clearly define the cases that can be brought to court, the procedures for handling claims, and the punishments for an offense. Civil law, which originated in France, is similar to common law in many ways. Both share the goal of establishing consistent outcomes by applying the same standards of interpretation to each case. However, civil law focuses more on the written codes and statutes and has a reduced emphasis upon established legal precedent.
Additional forms of law include customary laws, in which patterns of behavior or cultural customs have been accepted as legal requirements or rules of conduct, as well as religious legal systems, in which religious texts or traditions define that country’s laws. Religious legal systems are commonly seen in Islamic countries. Many countries have mixed legal systems that combine multiple legal systems into a single hybrid system. Finally, both the United States and Canada follow common law on a national level, but have a single region (Louisiana and Quebec, respectively) that uses a civil law system.
Countries with full common law include Anguilla, Antigua and Barbuda, Australia, Saint Helena, Ascension, Tristan da Cunha, Bahamas, Isle of Man, Saint Kitts and Nevis, Saint Lucia, Jamacia, Saint Vincent and the Grenadines, Barbados, Jersey, Belize, Bermuda, Singapore, British Virgin Islands, South Georgia and South Sandwich Islands, Cayman Islands, Tanzania, Christmas Island, Cocos Islands, Tokelau, Cook Islands, Montserrat, Trinidad and Tobago, Turks and Caicos Islands, Dominica, New Zealand, United Kingdom, Fakland Islands, Fiji, Niue, US Virgin Islands, Nortfolk Island, Northern Mariana Islands, Wake Island, Gibarltar, Grenada, and Guam.
Around 40 countries and territories use common law, and sixty more use common law in part.