Professor Emeritus of Public and Environmental Affairs at Indiana University, Bloomington. He previously served as Dean of the School of Public and Environmental Affairs and as Professor of Law in the Indiana University Maurer School of Law and has taught business law in the business schools at both Indiana University and Georgetown University. He has won teaching awards in both the School of Business and the law school. His teaching interests include commercial law, environmental law, alternative dispute resolution, law and public policy, and ethics and the public official. He is the co-author of several leading books on business law.

From 1985 to 1988, Professor Barnes served as the deputy administrator of the U.S. Environmental Protection Agency. From 1983 to 1985, he was the EPA general counsel, and in the early 1970s he served as chief of staff to the first administrator of the EPA. Professor Barnes also served as a trial attorney in the U.S. Department of Justice and as general counsel of the U.S. Department of Agriculture. For six years, from 1975 to 1981, he had a commercial and environmental law practice with the firm of Beveridge and Diamond in Washington, DC.

Professor Barnes is a Fellow in the American College of Environmental Lawyers and a Fellow of the National Academy of Public Administration. From 1992 to 1998, he was a member of the Board of Directors of the Long Island Lighting Company (LILCO). From 2004 to 2010, he chaired the Environmental Protection Agency's Environmental Finance Advisory Board. He was a member of the Department of Energy's Environmental Management Board from 2005 to 2011.