After his gubernatorial term ended, Parker devoted himself to his experimental farm at Bayou Sara near St. Francisville in West Feliciana Parish. In June 1929, he was named president of the Constitutional League of Louisiana, which was organized at the St. Charles Hotel in New Orleans to "save the state from Huey Long". State Senator Norris C. Williamson of East Carroll Parish became the vice-president of the 300-member group. Two other former governors, Jared Y. Sanders, Sr., and Ruffin Pleasant also spoke out against the Long political organization.