When can a bar legally refuse service to a customer?

A bar can legally refuse service to a customer when the customer is visibly intoxicated due to the responsibility of establishments to serve alcohol in a manner that promotes safety and compliance with Alcohol Beverage Control (ABC) laws. When a patron shows signs of intoxication, serving them alcohol may lead to increased risks such as disorderly behavior, potential accidents, or harm to themselves or others. In many jurisdictions, it's not only permissible but required for bars to refuse service to ensure the safety of all guests and to adhere to legal standards intended to prevent excessive drinking and related consequences.

The other options present scenarios that don't align with legal grounds for refusing service. For instance, refusing service solely based on busy hours would be considered discriminatory and not legally justified. Similarly, if a customer is behaving appropriately, there is no legal or safety rationale for denying them service. Lastly, whether a customer has a reservation does not provide sufficient cause to deny service; reservations are typically a courtesy extended by the establishment and do not relate to serving or not serving alcohol. Thus, the refusal of service based on visible intoxication is strongly supported by both ethical considerations and legal requirements in ABC laws.