The common law is the legal system which developed in England from the reign of Henry II in the 12th century and continues there and in former and current British territories and colonies. It was referred to as the common law because it was (and remains) common to all of England. The United States (except for Louisiana) and the United Kingdom are two prominent countries that have a common law legal system. The ICJ also uses common law.
The term is used to denote three distinct concepts:
1. Common law as opposed to statute law. That is, the law of precedent as opposed to the law expressed in legislation. In the common law countries judges will apply the common law in the absence of a statute governing a particular matter in issue.
2. Common law as opposed to Civil Law. That is, the common law legal system as opposed to the legal system adopted by most of continental Europe.
3. Common law as opposed to equity. That is, the law that applied in the former common law courts as opposed to that which applied in the former Court of Chancery. In England, the Judicature Act 1873 created a new system which gave the courts both legal (common law) and equitable jurisdiction.
Relationship to Islamic law
It has recently been pointed out that certain features of English Common Law bear a striking resemblance to Islamic law of the High Middle Ages, in particular to the Maliki School of jurisprudence. In particular, concepts such as trial by jury, land possession and perpetual endowment have no affinity with either Roman Law, which was becoming established in western Europe at the time, or with Anglo-Saxon local customary laws which preceded English Common Law, but have exact parallels in the Maliki legal system (e.g. the concept of a perpetual endowment in ECL is essentially identical to that of a waqf in Islamic jurisprudence).
A potential source of Islamic legal ideas was the court of Sicily, where the Norman rulers retained many customs and laws from the previous Muslim rulers, whose legal advisers were of the Maliki School. It has been noted that Thomas Brown, an English civil servant, worked in the Sicilian Court in the 12th century and later joined the court of Henry II of England at the very time that the Common Law was being established. Brown (known as Qaid Brun in Sicily), brought mathematical ideas from Sicily to England (e.g. the Arabic/Hindu numerals) and could equally have brought legal ideas as well, although there is no direct evidence that he did so.