ennis graduated from columbia university law school in 1932, and went on to work for the department of justice for fourteen years. he was a member of the national lawyers guild in the 1930s, but withdrew from the organization, believing it to be under the influence of communists. he held a variety of positions in the department of justice, including as general counsel for the immigration and naturalization service, director of the alien enemy control unit, and administrator of foreign travel control. his role made him the administrator of the japanese american internment. ennis chose not resign from his role at that time, but he did help american civil liberties union head roger baldwin to come up with legal strategies to oppose the internment, and testified at the trial of gordon hirabayashi about the department of war's withholding of evidence relating to japanese americans' loyalty to the united states.