Professor Grossman served as WCL dean from 1995-July 2016, at which time he decided to return to the faculty. He was appointed Dean Emeritus by American University's (AU) Board of Trustees in recognition of over two decades of commitment, dedication and distinction.

During Professor Grossman's 21-year tenure as dean, WCL further developed its intellectual creativity, pursuing numerous and exciting initiatives. More than 50 full-time faculty members were hired, dramatically improving the law school's student-faculty ratio and expanding and enhancing scholarship, teaching and service. A variety of WCL programs were developed during Professor Grossman's deanship including but not limited to: dual JD Programs with universities in countries, L.L.M. programs in Law and Government Program, Advocacy, Intellectual Property, along with specialized summer programs focused on international and humanitarian issues. Also during his leadership as dean, WCL developed and expanded summer abroad programs in Europe, Asia, and Latin America, numerous semester abroad programs, the International Commercial Arbitration Center, the Intellectual Property (IP) Program, clinics in IP, Disability Rights Law, Immigrant Justice and an evening section of the General Practice Clinic, and integrated sections in the first year so as to promote interconnectedness among the different law courses.

During Professor Grossman's tenure as dean, WCL achieved recognition as among the top 10 nationally in clinical legal education, intellectual property, international law, and trial advocacy, in addition to being one of the most diverse law schools in the country. With his leadership, WCL also designed and completed its magnificent new Tenley Campus, a state-of-the-art law school building just one block from the metro, connecting the law school's community to the nation's capital and its many professional opportunities.

Throughout his academic career, Professor Grossman has contributed to promoting the rule of law, human rights and legal education in both international and domestic organizations. Professor Grossman was elected to the United Nations International Law Commission in November 2016 for a five-year term, and previously served as member and chairperson of the United Nations Committee against Torture. On May 20, 2013, Professor Grossman was elected chair of the UN Human Rights Treaty Bodies for a one-year term. In May 2009, he was named to the judging panel for the Robert F. Kennedy Human Rights Award awarded by Robert F. Kennedy Human Rights, and in May 2010 he was appointed to the organization’s board of directors. Professor Grossman served on the governing board for the International Association of Law Schools since 2008 and was reelected in 2010 for a three-year term. On January 1, 2014, Professor Grossman began serving as President of the Inter-American Institute of Human Rights, following three years on its Board of Directors. He is also on the Board of the ABA’s Rule of Law Initiative (ROLI) and a member of numerous associations including the American Law Institute.

Professor Grossman has been consistently recognized as one of the top 25 most influential people in legal education. He has also received numerous awards for his work with human rights and international law, including the Harry LeRoy Jones Award from the Washington Foreign Law Society and the René Cassin Award from B'nai B'rith International in Chile.