[1][2] He was in private practice in Des Moines, Iowa from 1909 to 1942, except for his service during World War I as a lieutenant in the United States Army's legal department.
[2] After serving from 1942 to 1945 as a Special Assistant United States Attorney General and hearing officer for the Selective Service Bureau, Riley returned to his private practice with Carr, Cox, Evans, and Riley until 1950.
During the latter period, he also served as President of the Iowa State Bar Association from 1949 to 1950, and was active in the leadership of the American Bar Association.
[2][3] Riley was nominated by President Harry S. Truman on November 29, 1950, to a seat on the United States District Court for the Southern District of Iowa vacated by Judge Carroll O. Switzer.
His service terminated on December 29, 1956, due to his death.