 Mechem was appointed by Governor Otero as the district attorney for Quay and Guadalupe Counties of New Mexico, a position he held from 1905 to 1909, being reappointed by Governor Hagerman.He also served as a member of the New Mexico Territorial Council from 1909 to 1911.In 1909 President Taft appointed him a justice of the New Mexico Territorial Supreme Court where he served until 1911.