I believe you may be right about the state and the conscript laws. I have info on free Negro conscripts before and after 1862.
Now the Confederate Congress DOES NOT, to the best of my knowledge address the issue of armed soldiers. They do address all of the jobs that people normally think of slaves having-- teamsters, cooks etc. These jobs are listed as being part of the army.
Now that is not to say there were no armed Negroes, I, with the help of many others have been able to find and Id some of these Negroes. These are proven by many sources and are listed at SHAPES Negroes In Gray