Ms. Greenfield is a Senior Counsel for Appellate Matters at the Environment and Natural Resources Division of the U.S. Department of Justice. In this role, she supervises the defense of appellate challenges to U.S. Environmental Protection Agency rulemakings and other actions, and personally handles high-profile appellate matters as counsel of record. These challenges are brought in courts of appeals across the country under diverse environmental statutes including the Clean Air Act, the Clean Water Act, and others.

Professor Greenfield’s practice includes work on the appellate defense of EPA’s priority rulemakings. Representative cases include suits addressing EPA’s authority to regulate greenhouse gases under the Clean Air Act, EPA’s regulation of mercury from power plants, and the Agency’s regulation of coal-fired power plants under the Resource Conservation and Recovery Act. Professor Greenfield has argued nine cases in the federal courts of appeals, including six in the D.C. Circuit, and supervised dozens more. She regularly coordinates with the Office of Solicitor General on appeals of the matters she supervises. Professor Greenfield also detailed in the EPA Office of General Counsel, advising the Agency on rulemakings governing greenhouse gases and PFAS.

Before joining the Environment and Natural Resources Division, Professor Greenfield clerked for the Honorable Adalberto Jordan on the U.S. District Court for the Southern District of Florida, and then for the Honorable Ferdinand Fernandez on the U.S. Court of Appeals for the Ninth Circuit. She also worked as an associate in the Issues and Appeals Practice at Jones Day in Washington, D.C.