Here are a couple more comments on the standard of care of a tavern/bar to monitor alcohol consumption of its patrons:
"I recognize that it is not often possible for an establishment to assess whether a patron is intoxicated and, in many cases where there is not heavy consumption of alcohol in the establishment nor symptoms of intoxication, it would be unreasonable to expect an establishment to make that determination. On the other hand, service to a patron of the equivalent of between 16 1/4 and 19 1/2 fluid ounces of rye for his own consumption over a two-hour period carries obvious risks, and I am of the opinion that organization of service of alcoholic beverages, in the circumstances of this case, in a fashion which eliminated the opportunity to monitor the plaintiff's consumption constituted contributory negligence on the part of the hotel to the extent of five percent. Hotels are in the business of serving alcohol for a profit and it is not unreasonable for it to bear a portion of the risk caused by gross over-consumption." Goudge v. Three Top Investment Holdings Inc.,  O.J. No. 751 (Gen. Div.) at para. 52.
And here is comment from another case:
"I feel that they are liable both under the Liquor License Act and at common law. There is a high standard of care imposed on a tavern and its staff. The Squire Tavern people were oblivious to their duty. They knew these people were driving. They knew or should have known that they were intoxicated. They added to the level of intoxication by serving them more. I think that the standard maintained by the Squire was too low. Drinks would only be refused if the person was "too loud, starting arguments, knocking over drinks or falling down". Sambell v. Hudago Enterprises Ltd.,  O.J. No. 2494 (Gen. Div.).