Man in the Funny Hat
Hero
I had to add that one as a rule because one player would show up to the game at noon on Saturdays already half in the bag. And he was not an amusing, foolish guy when he drank; one who had us all laughing with his in-game hijinks. He was obnoxious and since he kept drinking after arrival, would only rapidly get worse. I instituted a No Drinking for anyone rule (which somewhat unfairly impacted a player or two who drank, but DIDN'T get drunk.) He started showing up already quite drunk, and only got irritable as he sobered up during the game. Soon after I just kicked him entirely. Had he not been my cousin he'd have been kicked MUCH earlier.I firmly believe it makes for a better and more enjoyable game - people don't take it as seriously, are more willing to laugh at their own foolishness, and are more willing to put their characters into ridiculous situations.(edit to add: that doesn't mean we get falling-down drunk)
Later, I had another player from the same group who was... dealing with work pressures by getting drunk nearly every weekend. He, however, managed to show up to games, play for at least some time without being disruptive, and then go quietly pass out in my living room and sleep it off. He did not need the rule enforced. But I retain the rule and the right to enforce it as necessary if I'm going to be the DM.