Seth is a graduate of St. John's University School of Law, where he served as an Executive Board member of the Moot Court Honor Society. He was a semi-finalist in the Hon. James F. Niehoff Civil Trial Competition and the Reverend Joseph Tinnelly Moot Court Competition. In his final year of law school, he was part of a three-member team which reached the quarter-finals at the Wagner National Labor & Employment Law Moot Court Competition held at New York Law School. During law school, Seth also completed internships at the Manhattan office of the National Labor Relations Board (Region 2) and the Brooklyn office of the New York State Public Employment Relations Board.

After graduation, Seth went into private practice representing labor unions and handling general litigation. A member of the New York State Bar Association, he is presently Chair of the Labor & Employment Law Section's Committee on Public Sector Labor Relations.