Right Joe, the Confederate government allowed non-citizens to be discharged (I believe) after the first consription law passed. Those that were British subjects were given a parole papers to cross the lines and go back home if they wished. But, after crossing over to the Union side they were subject to being arrested or detained.

"Life In The Confederate Army Beging the Observations and Experiences of an Alien in the South" by William Watson of Glasgow Scotland, (who's son was a hero in the Boer War).