SBT - if, as I surmise, you do not want to go 'official' with this, I suggest you lay down your flightdeck 'policy' CLEARLY at the briefing stage. It is your flight deck to manage, and assuming you are not operating outwith SOPs and 'normal' procedures, put it to him that if he does not accept that there neeeds to be a chat with management. He has, after all, presumably managed to read Part A by now?
Certainly hearing YOUR side of it, it sounds quite unacceptable behaviour.