 While he was an Assistant to the Solicitor General in the Department of Justice under Solicitors General Archibald Cox and Thurgood Marshall, he argued 12 cases before the Supreme Court of the United States.Lewin's Supreme Court cases included the representation of banks and other commercial interests as well as criminal cases and issues of constitutional law.In 2012, the Supreme Court ruled in his favor in the case of "Zivotofsky v. Clinton", holding that the political question doctrine does not deprive a federal court of jurisdiction to enforce a federal statute that explicitly directs the Secretary of State how to record the birthplace of an American citizen on a Consular Report of Birth Abroad and on a passport.