You can't do the course with the usb unpluged every now and then a stelth pulse is sent to check the device is being worn the wearer needs to confirm when this is recieved if for some reason the steath pulse is not recieved the course will know.
I'm surprised that no one has yet answered this question. The computer could no longer transmit random stealth pulses for the user to acknowledge. additionally (And this was my initial assumption) you can also turn on leash mode (confine to PC) in the DL browser or through the DL lounge. The only question is: can the user simply plug it back in?