People

Andrew Mergen is a Visiting Assistant Clinical Professor of Law and Faculty Director of the Emmett Environmental Law & Policy Clinic. Prior to joining the Harvard Law School faculty, Andrew Mergen served in the Appellate Section of the Environment & Natural Resources Division (ENRD) at the United States Department of Justice. Professor Mergen began his career at the Justice Department in the Honors Program and concluded his career as Chief of ENRD’s Appellate Section. He has presented oral arguments in all 13 federal courts of appeals, including two en banc courts, and before several state intermediate and supreme courts. He has also worked on over a dozen merits cases in the Supreme Court of the United States. In addition, in 2009, Professor Mergen assisted the Office of White House Counsel on the confirmation of the Honorable Sonia Sotomayor as Associate Justice of the Supreme Court. During his career at the Justice Department, Professor Mergen received the Attorney General’s Award for Distinguished Service three times. He also received ENRD’s Muskee-Chafee Award, honoring his work’s significant contribution to protecting the environment. Before entering clinical teaching, Professor Mergen taught at several law schools including, Harvard Law School (Advanced Environmental Law), the University of Michigan Law School (Natural Resources Law) and the William S. Richardson School of Law, University of Hawaii-Manoa (Administrative Law). Professor Mergen has written about federal water rights in “A Misplaced Sensitivity: The Draft Opinions in Wyoming v. United States” (68 Colo. L. Rev. 683 (1997), with Sylvia F. Liu); energy development on public lands in “Surface Tension: The Problem of Federal Private Split Estates” (33 Land & Water L. Rev. 419 (1998)); climate change and the Endangered Species Act in “The Role of Climate Change in ESA Listing Decisions” (53 Rocky Mt. Min. L. Fdn. 67 (2016), with Murray Feldman) and the accommodation of Native American sacred sites on federal land in “Finding the Path Forward for Indigenous Sacred and Cultural Spaces on Federal Public Land,” 68 Nat. Resources & Energy L. Inst. 32-1 (2022). Professor Mergen is a graduate of the University of Wisconsin—Madison and the George Washington University Law School.

Sommer Engels joined the Emmett Environmental Law & Policy Clinic as a Clinical Instructor in August 2023. Sommer previously served as an attorney in the Appellate Section of the Environment & Natural Resources Division at the U.S. Department of Justice (DOJ) for six years. Her cases covered numerous pollution control and natural resource management statutes and touched on a range of jurisdictional and constitutional issues. Sommer authored 25 merits briefs and dozens of substantive motions and memoranda, and she presented 15 oral arguments in federal appellate courts across the country. She was also one of the Appellate Section’s law clerk program coordinators and has extensive experience working with and training law students. In addition to her litigation experience at DOJ, Sommer was detailed to the White House Council on Environmental Quality early in the Biden Administration, where she served as Deputy General Counsel. She advised the Chair and other White House officials on the legal implications of environmental initiatives and emergencies nationwide, co-managed an interagency group tasked with developing guidance for federal agencies on Traditional Ecological Knowledge, and helped ensure that proposed regulations were consistent with the Administration’s environmental justice initiatives. Prior to joining DOJ, Sommer was a law clerk for Judge Bruce M. Selya on the U.S. Court of Appeals for the First Circuit. Sommer graduated from the University of Michigan Law School in 2016 and was the managing editor of the Michigan Law Review. She received her B.A. from Colby College.

Aspen Ono joined the Clinic as a Clinical Fellow in Fall 2025. Before that, she served as a law clerk for Judge Gina R. Méndez-Miró of the U.S. District Court for the District of Puerto Rico and Judge Robert S. Ballou of the U.S. District Court for the Western District of Virginia. Aspen earned her J.D. from the University of Virginia School of Law in 2023, where she participated in the Environmental Law and Community Engagement Clinic and was active in the Virginia Environmental Law Forum, Virginia Law Women, and UVA Women of Color. She holds a B.A. in environmental science and international relations from Emory University and an M.A. from the University of British Columbia’s Institute for Resources, Environment and Sustainability, where her research focused on improving access to urban green spaces for marginalized migrant communities.

Jacqueline Calahong is a staff assistant for the Emmett Environmental Law & Policy Clinic. Jacqueline has worked at the Tufts University Center for Children, Ceres, Massachusetts Department of Environmental Protection, and Public Employees for Environmental Responsibility. She holds a B.A. in political science from the University of Michigan and a J.D. from the Pennsylvania State University Dickinson School of Law.