From Wikipedia:
Case law is the reported decisions of selected appellate and other courts (called courts of first impression) which make new interpretations of the law and, therefore, can be cited as precedents in a process known as stare decisis. These interpretations are distinguished from statutory law which are the statutes and codes enacted by legislative bodies; regulatory law (a.k.a. administrative law) which are regulations established by governmental agencies based on statutes; and in some states, common law which are the generally accepted laws carried to the United States from England.