What is the primary source of reference in common law when making legal decisions?

In common law, the primary source of reference when making legal decisions is historic cases and precedents. This system is characterized by the principle of stare decisis, which means "to stand by things decided." Courts rely on prior judicial decisions to resolve similar cases, ensuring consistency and stability in the law. When judges encounter a new legal issue, they look to previous rulings to guide their decisions. This reliance on case law distinguishes common law from civil law systems, which primarily focus on codified statutes.

The other choices represent important aspects of the legal framework but do not serve as the primary reference source in common law. Statutes, while critical, are interpreted and applied through the lens of existing case law. Legal commentaries provide insights and analyses but are not binding. International treaties, although significant in certain contexts, do not form the foundation of domestic common law decisions. Thus, the weight given to historic cases and precedents is what solidifies their role as the primary resource in common law.