Examine Chevron v. NRDC, the seminal case on the weight courts should give to a federal agency’s interpretation of a federal statute. Then, take a closer look at two other cases that offer a sense of how courts approach statutory ambiguity—MCI Telecommunications v. AT&T and FDA v. Brown & Williamson Tobacco. Conclude by considering the complicated interaction among legislatures, courts, and government agencies by which U.S. law and policy are implemented.