Better yet, why did the captain ever let the flight leave? Protect your crew from their own stupidity. Pull of a placard, ground the damn thing. I would think that if you took off knowing the other guy was intoxicated on an aircraft that requires two crew members makes you a party to the crime and at the end of the day can end up burning you as well. If the guy really wants to fly drunk, don't take off, don't push off. Get it taken care of.