Common law
The common lawso named because it was "common" to all the king's courts across Englandoriginated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire spread the English legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, and to the style of reasoning inherited from the English legal system.
Constitutional law
The common law and the civil law jurisdictions do not share the same constitutional law underpinnings. Common law nations, such as those in the Commonwealth as well as the United States, derive their legal systems from that of the United Kingdom, and as such place emphasis on judicial precedent, whereby consequential court rulings (especially those by higher courts) are a source of law. Civil law jurisdictions, on the other hand, place less emphasis on judicial review and only the parliament or legislature has the power to effect law. As a result, the structure of the judiciary differs significantly between the two, with common law judiciaries being adversarial and civil law judiciaries being inquisitorial. Common law judicatures consequently separate the judiciary from the prosecution, thereby establishing the courts as completely independent from both the legislature and law enforcement. Human rights law in these countries is as a result, largely built on legal precedent in the courts' interpretation of constitutional law, whereas that of civil law countries is almost exclusively composed of codified law, constitutional or otherwise.