When it's operated at a distance greater than what the natural line of site permits. When it requires a gps navigation system to maintain course and altitude. When it requires an onboard and downlinked telemetry systems to monitor flight systems and navigation. When it is navigated by a means other than direct visual reference between the operator and the aircraft. When onboard video is used to navigate the aircraft. Plus the rules from the FAA already noted.

You don't want to get caught doing uav stuff outside the boundaries of current regulations. It goes FAR beyond the FAA when the explaining has to get done.