The Army of the Tennessee was ordered TO plunder. Conversely the Army of NoVa was order NOT TO plunder. Of course some in the AofNoVa violated the orders and when caught were PUNISHED.
The Army of Northern Virginia was ordered not to requisition anything without the empty formality of offering worthless Confederate government IOUs first.
So, clearing aside the technical language, both armies were ordered to take whatever they felt like taking. And they did. With both hands.