Even when not on active duty orders - reservists and guardsmen are still subject to command structure and the UCMJ.
Since guardsmen and reservists are citizens first, soldiers second they are able to keep their civilian jobs and serve when on orders. There are many elected officials that serve in the guard and reserve. LG could serve in the senate and also perform guard duties when on orders.
In any conflicts LG would not attend a vote or recuse from JAG duties as appropriate.
As many have realized to their chagrin.