Originally Posted by
43Inches
< snip > Going back to the original post, if the instructor was PIC he would be within his rights to ask for pre-flight checks to be conducted as he wished, including run-ups, because he is legally responsible should something happen on take-off and the run ups would have uncovered such a fault. If the candidate was PIC, then the instructor can ask the run-ups be done, if not complied with satisfactorily then they can either accept it and continue, state they wish to terminate the check and make it training or ask to be returned to the school and terminate the check. What happens next could be touchy as then it would come down to being a failed AFR and the candidate would not then be able to exercise the privileges of their licence, or part there of that was not completed.
I think you'll find that the OP's scenario was the other way 'round: The instructor told the owner not to do run-ups the owner wanted to do.