With the exception of two periods of United States Government service, Harris Weinstein practiced law with Covington's Washington office as an associate, partner, and senior counsel between 1962 and his retirement from practice in 2009. He was with the Department of Justice during the period 1967-1969 as an Assistant to the Solicitor General of the United States and with the Department of the Treasury during 1990-1992 as Chief Counsel of the then Office of Thrift Supervision. Before joining Covington, Harris was law clerk to Judge William H. Hastie of the United States Court of Appeals for the Third Circuit.

His private practice focused on civil litigation, including disputes under antitrust, securities, tax and banking laws, and patent and related trade issues. He has appeared in federal trial and appellate courts throughout the United States and, as a government attorney, argued nine cases in the United States Supreme Court.

From January 2007 through December 2016, Harris served as a Distinguished Lecturer on the faculty of the Columbus School of Law of The Catholic University of America, teaching International Commercial Arbitration as well as other subjects. He also coached the law school’s team in the Willem C. Vis International Commercial Arbitration Moot. He has taught the arbitration course at the University of California, Davis and lectured on the subject at Penn State Law School and the University of Lisbon, Portugal.

Harris’s teaching activity has included lectures on banking law or corporate fiduciary issues at American University, George Washington University, and the Universities of Illinois, Michigan and Virginia. He has also taught one-week courses on Banking and International Arbitration under United States Law as part of Catholic University’s American Law program at the Jagiellonian University in Krakow, Poland.

In his pro bono work, Harris was a member of the Administrative Conference of the United States and chaired the Conference’s Committee on Government Processes. He also has been a member of the Corporation of the Massachusetts Institute of Technology, President of its alumni/ae association, and Chair of its Alumni/ae Fund; Counsel to the Contests and Credentials Committees of the Republican National Conventions of 1984 and 1988; and a member of the initial advisory committee of the Commonwealth Institute (Richmond, VA).

His law degree is from Columbia University, where he was editor-in-chief of the Columbia Law Review. He received S.B. and S.M. degrees in mathematics from M.I.T. and was elected an associate member of the Sigma Xi science honorary society.