He attended Centre College in Danville, Kentucky, and subsequently the United States Military Academy at West Point, New York.

He was promoted to the temporary rank of Lieutenant Colonel during World War I and was assigned to the Office of the Provost Marshal, where he served as a Chief of Mobilization Division.

In 1919, Gullion was transferred back to the United States and was appointed the legal adviser of major general Robert Lee Bullard on Governors Island.

Gullion was a prime mover in the efforts to intern American citizens of Japanese ancestry in camps in the wake of the hysteria resulting from the Pearl Harbor attack.

In 1943, the FBI investigated Gullion for his role in forming an extra-military organization known as the SGs which was intended "to save America from FDR, radical labor, the Communists, the Jews, and the colored race.