He is a retired partner at Simpson Thacher & Bartlett LLP, a former president of the New York City Bar Association, and an emeritus member of the Council of the American Law Institute.

Harper received a Bachelor of Arts degree cum laude from Howard University, where he was elected to Phi Beta Kappa.

1, Denver, the first case in which the United States Supreme Court ruled on de facto school segregation that had not been ordered by law.

He served as the City Bar's first African-American president from 1990 to 1992, where he worked to increase ethnic and gender diversity within the Association's committees and governance.

He has served as an Adviser on several ALI law reform projects, including Recognition & Enforcement of Foreign Judgments, and Transnational Rules of Civil Procedure.