Perhaps the largest single body of law in existence is that of case law.
Case law is that law as interpreted and set forth by appellate courts or courts of review.
In performing this function appellate courts have the opportunity to pass on the constitutionality of any laws that were challenged and to interpret and determine the legislative intent that underlies statutes. In those cases where there is no constitutional rule or legislative enactment that applies, the appellate courts apply the rules of common law, i.e., the law as derived from our system of Anglo-American jurisprudence, to decide which rules or principles are necessary to resolution of the issues at hand.