Originally Posted by
Checkboard
I would say you absolutely can't do that, or "PIC" has no meaning. I think you'll find the "flight" is defined from start to stop, and thus the PIC is for that flight. Once the PIC is designated for the flight, that's it until you land - regardless of if the owner is on board or not. It's irrevelant if the owner happens to have a licence.
If there is conflict the best the candidate can do is ask the PIC to terminate the flight. Unless there was a handling issue, most instructors would leave control to the candidate.
It would be a very courageous instructor who denied a request to terminate the session. Anyone who did would certainly deserve to be reported for misconduct and whatever else.