Professor Highsmith served for 30 years as an attorney at the U.S. Department of State, with primary responsibility for legal issues related to arms control and the nonproliferation of weapons of mass destruction and missiles. He headed the legal office responsible for such issues from 2002 to 2013 before taking on broader responsibilities as a Deputy Legal Adviser from 2013 to 2017. He retired in April 2017. During his career, he served as primary or sole legal adviser on the U.S. delegations that negotiated the 1994 Agreed Framework with North Korea, the 2008 Agreement for Nuclear Cooperation with India, and the 2015 Joint Comprehensive Plan of Action with Iran. In addition, he was directly involved in: negotiating the New START strategic nuclear weapons treaty with Russia; analyzing the legal issues raised by Syria’s use of chemical weapons and its construction of a clandestine nuclear reactor; establishing export control guidelines in the Nuclear Suppliers Group; responding to Indian and Pakistani nuclear testing; facilitating Libya’s renunciation of weapons of mass destruction; and responding to the revelations regarding Iraq’s nuclear weapons program. He was responsible for the legal interpretation of numerous arms control and nonproliferation statuses and treaties, including the Nuclear Nonproliferation Act, the Statute of the International Atomic Energy Agency, the Nuclear Nonproliferation Act, relevant UN Security Council resolutions, and various U.S. sanctions laws. Prior to joining the State Department, he worked in private practice for three years and was a Teaching Fellow at George Washington Law School for two years.