I witnessed this: a player who burnt the candle at both ends fell asleep during the game and his friend woke him up. His opponent vehemently objected. How should this have been handled?
I do not recall if his friend simply shook him awake or used the pretext of bringing him a sandwich -- the latter I do not think could be objected to nor if a phone call had been made to the site asking for a player (Does a director tell the a player during a game if a non-emergency call is received? this was pre-cell phone.)
I do not recall how the director handled things. Forfeiting the sleeper seems extreme -- a warning, which does nothing except if the director said, "if this happens again and your friend wakes you up I consider this illegal aid and I will forfeit you."
The opponent wanting to win that way seems more than a little unsportsmanlike but if the official rule is that not only can a third party not wake someone but even his opponent can't, then rules should be observed.
My opinion: I think the rulebook should explicitly say that waking someone should be allowed and even the director can do this. Maybe the rules do this.