University of Michigan Law School dean

In 1994, Lehman became Dean of the University of Michigan Law School], where he was at that time the youngest law school dean in the U.S. During his deanship, Michigan became the first U.S. law school to require all J.D. students to complete a course in transnational law. The school also drew attention for initiatives in public service and the teaching of legal writing. From 2001 to 2003, he served as president of the American Law Deans Association.

Along with then-University President Lee Bollinger, Lehman received national attention in the 2003 Supreme Court case of Grutter v. Bollinger in which the University largely succeeded in defending the law school's affirmative action admissions policies.

Cornell University president

In 2003, Lehman became the 11th president of Cornell University. As president of Cornell, he oversaw effective large-scale fundraising efforts. In 2004, Cornell ranked third in the nation in university fundraising (behind only Harvard and Stanford), raising over US$375 million that year alone. Lehman was also known for prominently promoting his "three themes": "life in the age of the genome," "wisdom in the age of digital information" and "sustainability in the age of development." These themes arose from intensive engagement with faculty, students and Cornellians during his first year, a process that won him great respect across campus. Lehman pioneered the concept of a "transnational" university, by opening a medical campus in Doha, Qatar and cooperative education and research arrangements with universities in China, India and Singapore.

In 2005, Lehman resigned from the presidency, citing irreconcilable differences with the leadership of the Cornell Board of Trustees — an announcement that came as a surprise to most of the Cornell community and to outsiders. Lehman's tenure was by far the shortest of any Cornell President until the death of Elizabeth Garrett in 2016. Specific reasoning for Lehman's departure has been highly secretive and subject to occasional debate within the Cornell faculty and alumni communities.

Lehman remained a member of the Cornell Law School faculty until 2012.^[5] In 2007, Cornell published An Optimistic Heart, a book of speeches that Lehman wrote and delivered as president.

Peking University School of Transnational Law dean

After serving as a senior scholar at the Woodrow Wilson International Center for Scholars in Washington, D.C., Lehman became the chancellor and founding dean of the Peking University School of Transnational Law, located on the university's Shenzhen campus. The school is modeled on the American style of law school, and it is intended that graduates will be eligible to sit for the New York bar exam.^[6] On Sept. 29, 2011, Lehman was a recipient ^[7] of the 2011 Friendship Award, China’s highest award for foreign experts who have made outstanding contributions to China’s economic and social progress.

NYU Shanghai founding vice chancellor

In April 2012, it was announced that Lehman would be steering the new institution jointly with Yu Lizhong, former president of New York University's local partner, East China Normal University. "Yu will be the chancellor and will play a major role in government relations. ... Lehman, as vice chancellor, will have free rein in academic affairs. The first students will arrive in fall 2013, the majority of them from China." In the time from summer, 2012 until opening, Lehman is dividing his time between New York and Shanghai.^[8][9]

Other professional activities

From 2007 to 2011, Lehman chaired the board of Internet2, an advanced not-for-profit U.S. networking consortium led by members from the research and education communities, industry, and government.

From 2006 to 2017, Lehman was an independent director of Infosys, Limited, a NASDAQ listed technology company headquartered in Bangalore, India.

During 2020 and 2021, Lehman chaired the board of the American Chamber of Commerce in Shanghai.