John Nonna fenced at Princeton, graduating in 1970, and represented the New York Fencers Club. He later received a law degree from New York University. Nonna became a practicing attorney specializing in insurance law, commercial litigation, and arbitration, working for the international law firm Patton Boggs. Nonna served a term as mayor of Pleasantville, New York and was a Westchester County Legislator, where he served as Chair of the Legislation Committee and a member of the Energy and Environment, Housing and Planning and Public Safety Committees. He is a Fellow of the American College of Trial lawyers, and has been active in the New York State Bar Association, serving as Chair of the Commercial and Federal Litigation Section, as a member of the House of Delegates, and as a Chair of the Federal Legislative Priorities Committee.
United States