It's a player rule. They bought in to it, even if it was set 5 years ago.
If the players don't like it, get rid of it.
Or change it. If the players think, based on the advice they receive, that "X standard drink N nights before the game is acceptable", then they can change it to that.
If the players want to keep it, then keep it and stick to it.
Maybe they will change it after this incident, or after this season.
Maybe they won't.
But stick by the rules you set yourself, or it's a slippery slope.