Mandelker is the Stamper Professor of Law at Washington University in St. Louis, where he teaches environmental law and land use law. He is co-author of casebooks on environmental law and land use law. Mandelker was the principal consultant to the American Planning Association's Growing Smart project, which published new model planning and zoning legislation to replace existing planning and zoning acts. He is the author of a chapter on integrating environmental reviews with land use planning at the state level. He has lectured widely on the National Environmental Policy Act (NEPA) and land use topics and was the consultant to the sections of State and Local Government and Administrative Law in the preparation of model land use legislation for administrative and judicial review for adoption by the House of Delegates.