Paroled prisoners were returned to their side, but were prohibited by
an oath of honor from taking up arms or performing any duty that soldiers
normally performed (like garrison or guard duty) until they were properly
exchanged. Generally each side maintained parole camps where their
paroled soldiers were kept while they awaited exchange, but in other cases
the parolee was allowed to return home until exchanged.
[Sources: Boatner, Civil War Dictionary; Miller, ed, "Prisons and
Hospitals", vol 8, Photographic History of the Civil War]