Barrett was born in Lusk, Wyoming to Frank A. Barrett and Alice Catherine Donoghue Barrett. He graduated from Niobrara County High School in Lusk in 1940. As a teenager he wrote for the "Lusk Herald" and The Denver Post. He served in the United States Army during World War II from 1942 to 1945, where he participated in the Invasion of Normandy. He was assigned to the Headquarters Detachment of the 1st Army and 3rd Army and achieved the rank of corporal. After the war, he attended Catholic University of America in Washington, DC for six months. He entered law school in the fall of 1946, he went to University of Wyoming College of Law and received a Bachelor of Laws in 1949.

He was in private practice in Lusk from 1949 to 1967, serving as a prosecuting attorney in Lusk from 1951 to 1962, and as a town attorney from 1954 to 1956. He was secretary-treasurer of Niobrara County Republican Central Committee from 1950 to 1966, and the attorney for the Niobrara Consolidated School District from 1952 to 1962. He became the Wyoming Attorney General from 1967 to 1971.^[1]

On March 25, 1971, Barrett was nominated by President Richard Nixon to a seat on the United States Court of Appeals for the Tenth Circuit vacated by Judge Joe Hickey.^[2] Barrett was confirmed by the United States Senate on April 21, 1971, and received his commission on April 23, 1971. He served as a Judge of the United States Foreign Intelligence Surveillance Court of Review from May 19, 1979, to May 18, 1984. Barrett had a reputation as a staunch conservative and dissented when the Court found that an Oklahoma law banning teachers from publicly supporting gay rights was unconstitutional. Barret called homosexual conduct “unnatural and detestable” and said that advocacy of it was less deserving of Constitutional protection than “advocacy of violence, sabotage, and terrorism.”^[3] He assumed senior status on April 8, 1987, serving in that status until his death.^[1]

Barrett's father, Frank A. Barrett, was a member of the United States House of Representatives, United States Senate, and the 21st Governor of Wyoming. Barrett was married to Carmel Ann Martinez Barrett and they had three children.^{[citation needed]}

Barrett died on November 7, 2011, in Cheyenne, Wyoming. He is interred at Lusk Cemetery in Lusk, Wyoming.

• List of United States federal judges by longevity of service

• James Emmett Barrett at the Biographical Directory of Federal Judges, a publication of the Federal Judicial Center.
• The Political Graveyard