What does case law primarily consist of in the context of the U.S. legal system?

Case law primarily consists of decisions by federal and state courts because it encompasses the body of existing law established by the rulings and interpretations made by judges. This includes not only the high-profile decisions made by the U.S. Supreme Court, which set important precedents for the entire nation, but also the rulings from lower federal courts and various state courts that can interpret statutes and legal principles relevant to their jurisdictions.

The importance of case law lies in its role in shaping, clarifying, and sometimes altering the application of statutory law through judicial interpretation, thereby providing precedents that guide future court decisions. These decisions help fill gaps where legislation may be silent or ambiguous, and they establish legal principles that influence not only similar cases but also the development of law as a whole.

Other choices focus either too narrowly on specific courts or bodies of law, failing to capture the comprehensive nature of case law that derives from both federal and state judicial systems.