Which of the following is NOT a source of law in the United States?

Contractual agreements are indeed an important aspect of the legal landscape but are not classified as a source of law in the same way that statutes, international treaties, and common law are.

Statutes are laws enacted by legislative bodies, defining legal obligations and prohibitions. International treaties represent agreements between nations that govern aspects of international law and can influence domestic law, especially when they are ratified. Common law, derived from judicial decisions and precedents established in court cases, evolves over time and shapes legal principles through interpretation.

In contrast, contractual agreements are more about the mutual consent of parties involved and do not create generalizable legal rules applicable to everyone. Instead, they are specific to the parties in a contract and rely on the foundational sources of law (like the aforementioned statutes and common law) to be enforceable in a legal context. While they are legally binding, they represent an application of existing law rather than a source of law itself. This distinction is critical in understanding the different roles various legal elements play in the U.S. legal system.