Which of the following is NOT a source of U.S. law?

Business ethics is not considered a source of U.S. law because it pertains to the moral principles and standards that guide behavior in the business context, rather than being codified laws or regulations enforced by the government. While ethical considerations can significantly influence business practices and decision-making, they do not carry the same legal weight as laws established through formal legal systems.

On the other hand, administrative law, case (common) law, and statutory law are all recognized sources of U.S. law. Administrative law consists of regulations and rules created by government agencies; case law, or common law, is developed through judicial decisions where courts interpret and apply the law; statutory law encompasses laws enacted by legislatures. These sources collectively form the framework within which legal standards and rules are set in the United States, indicating that business ethics, while important, falls more into the personal and organizational values category rather than a legal one.