Landis served as a member of the Federal Trade Commission (1933–1934), as a member of the Securities and Exchange Commission (1934–1937), and as chairman of the Securities and Exchange Commission (1935–1937). While dean of the Harvard Law School from 1937 to 1946, Landis served as regional director of the U.S. Office of Civilian Defense (1941–1942) and then as its national director (1942–1943). President Franklin D. Roosevelt then sent him to Egypt as American Director of Economic Operations in the Middle East (1943–1945).