Establishments that serve alcohol have a positive duty to intervene to limit alcohol consumption or risk liability.
Here is the classic formulation:
"I agree that establishments which serve alcohol must either intervene in appropriate circumstances or risk liability, and that this liability cannot be avoided where the establishment has intentionally structured the environment in such a way as to make it impossible to know whether intervention is necessary. Such was the situation in Canada Trust Co. v. Porter where the alcohol was served from behind a bar and it was impossible for the establishment either to monitor the amount consumed or to determine whether intervention was necessary. A similar situation arose in Gouge v. Three Top Investment Holdings Inc.,  O.J. No. 751 (Ont. Ct. (Gen. Div.), where the plaintiff attended a company Christmas party which had a "cash bar", over-indulged, and then was involved in an accident. In such circumstances, it would not be open to the establishment to claim that they could not foresee the risk created when the inability to foresee the risk was the direct result of the way the serving environment was structured."
Stewart v. Pettie,  1 S.C.R. 131 at para. 56.