I'm with 'chimbu'on this one but either way I think some common sense should prevail here in the lack of any actual Co SOP's/Regs.
If you where a Capt in 'pornstar' for Eg & you had a 250hr low hr'd cadet F/O at the steering wheel whilst you where in the little boys room just how long do you really think you would sit there? 2 splashes & yr back like a flash I'd say!
Wmk2