 After the war, Gross rejoined the State Department, serving as Legal Adviser of the Department of State and as deputy to the Assistant Secretary of State for Occupied Areas (Gen. John H. Hilldring, then, from 1947, Charles E. Saltzman).In 1948, Gross signed the Convention on the Prevention and Punishment of the Crime of Genocide on behalf of the United States.From March through October 1949, Gross was the Assistant Secretary of State for Legislative Affairs.