James studied law and was admitted to the Huntsville bar in 1846.
Phelan was apprenticed at the age of fourteen on the Huntsville Democrat, where he remained employed until 1842. In 1842, he edited Flag of the Union, the Democratic organ of Tuscaloosa. The following year he was named state printer.
He studied law and was admitted to the Huntsville bar in 1846, where he practiced until he moved to Aberdeen, Mississippi, in 1849. Until 1861, he was a famous lawyer in Aberdeen. In 1860, he was elected as a secessionist to the Mississippi Senate. Phelan served in the first Confederate Senate.
Phelan served on the Indian Affairs, Judiciary, Printing, and Conference Committees. He later served as a presiding military court judge for the remainder of the war.
After the war he was impoverished. He returned to his law practice in Alabama and later moved to Memphis, Tennessee, in 1867. James practised law in a firm formed with Henry T. Ellett.
Phelan was a personal friend and advisor to Jefferson Davis. He introduced a bill authorizing the impressment of all cotton in the South. That action probably cost him his seat in the Senate. His friendship with Davis and the support of Bragg were also upsetting to his constituents.
On September 22, 1846, Phelan married Eliza Jones Moore.