Currently it appears that you can still have limited control of a vessel even if out of range - you can set SAS to any of the default points, use max throttle, and do part actions like science experiments, solar panel deployment and staging by right clicking the part and doing the action via the parts menu.
Is there a way to disable this and leave an unconnected vessel completely dead in the water so I'm not tempted to "cheat" when my probe is out of range? I didn't see an option for this in the mods menu.