"The latter, by instructions from the War Department to General Holmes, were allowed to remain as part of his command, and formed so large a proportion of the effective force of the Arkansas troops that their removal would have been equivalent to breaking up some of the best organizations in that district. The former were collected and organized soon after the fall of the post. in some cases nearly entire companies and regiments had escaped capture. No order had ever been published transferring them from the department. They were regularly on duty here when the exchange of their comrades was effected at City Point and information had been received that the Arkansas Post prisoners had left Richmond under orders to return to this department."
General Kirby Smith.
Furloughs are not a duty assignment but a temporary relief from duty. Also it was not a guarantee to receive a furlough but customary for different circumstances. Duty assignment orders by department is clearly what General Smith was referring to in these statements. Lee did not have control of the men from the Trans-Mississipppi Department, he would have had to ask (beg) for these troops via Richmond.