You guys are all wet on this one and I totally disagree.
The Mount Washington is a State of NH alcoholic beverage licensed premise. Their license requires that they do not sell alcoholic beverages to people under the age of 21, or to someone who is no longer sober. The licensed premise has to undergo training in determining how to tell when someone is no longer sober,
These laws are in place to protect both the individual drinker himself and the public, and have been developed over the years, in large part, to put a stop to drunk drivers.
As a licensed premise, the Mount Washington has a legal obligation to follow the rules of their license.
By shutting someone off at the bar, it means the licensed premise is not making a sale and the bartender is not making a tip, so there is plenty incentive here for them to keep pouring those drinks.
Maybe someone could find the State's rules for alcohol licensees that apply here? As we all know; "Ignorance of the law is no excuse!