Terry, most States of the Confederacy had laws against militia or even State troops doing the follow:
"Crews from the Naval Iron Works were sent to install or repair Navy ships’ machinery at various bases all over the lower South. John Henry was part of these repair/installation parties. In 1864 John Henry Stanford became ill at the Mobile, Alabama Naval Yard while repairing a boiler. He was brought home, where he soon died of consumption (tuberculosis) at the age of nineteen."
Generally, militia could not leave the county in which they served. State Troops could not leave the State in which they served. Without further evidence, I'd assume that Georgia had these same laws. I seem to recall some big row with the Georgia Governor over this very issue.
By those indications, these had to be part of a Confederate National unit.