Can a social host be held liable for a guest's negligence after drinking at their party in Ontario?

Generally, no. Canadian courts, including in Ontario, have been reluctant to impose a duty of care on a purely social host - someone hosting a private party where alcohol is served - for injuries later caused by an intoxicated guest, such as in a car accident after the guest leaves the event. Courts have distinguished this situation from commercial hosts, like bars and restaurants, which profit from alcohol sales, are subject to specific regulatory obligations, and generally have more practical ability to monitor and control how much a patron consumes.

Part of the reasoning is that a private host typically does not have the same means of tracking a guest's consumption throughout an evening, and courts have expressed concern about the very broad and difficult-to-manage liability that would follow from treating every social gathering as creating this kind of duty. That said, courts have left open the possibility of liability in unusual circumstances, such as where a host actively created or significantly contributed to a specific, known danger beyond simply serving alcohol at the event. This remains a narrow, fact-dependent exception rather than a general rule imposing liability on social hosts.