A Jutsu created by the Sound Ninja Four.
Basically its the same thing as releasing a Genjutsu. If someone is able to touch the stolen Soul with Chakra then the Soul can come back from behind the Barrier. Even the System we have at HQ cannot pinpoint the exact location where they are being held. We assume the enemy is using a Special Barrier. And the souls of Shikamaru's and the others are trapped inside. But unless I know where the Barrier is there is no way I can communicate with them. There is just no way to find a Soul that is separated from its physical body.