 Lewin was law clerk to Chief Judge J. Edward Lumbard of the United States Court of Appeals for the Second Circuit (1960–1961) and to Associate Justice John M. Harlan of the Supreme Court of the United States (1961–1962).Lewin also served as Deputy Administrator of the Bureau of Security and Consular Affairs at the Department of State.He later served as Deputy Assistant Attorney General in the Civil Rights Division of the Department of Justice.