What is the most valid reason for refusing service to a patron?

Refusing service to a patron who is obviously intoxicated by alcohol is grounded in both legal and ethical considerations within the alcohol service industry. Serving alcohol to someone who is already intoxicated can lead to dangerous situations, including increased risk of accidents, health issues, or legal repercussions for both the server and the establishment. Responsible service of alcohol aims to ensure the safety of all patrons, and recognizing signs of intoxication is a key component of this responsibility.

In many jurisdictions, there are laws that specifically prohibit serving alcohol to intoxicated individuals, making this decision not only ethical but also a necessary legal obligation. By refusing service in this instance, you are helping to promote a safe environment and adhere to the regulations governing alcohol service.

Other reasons provided in the options might have validity in certain contexts, but they do not carry the same level of immediate risk to safety and legality as serving someone who is already intoxicated. For instance, while serving someone under 21 years old is also a serious matter, the act of intoxication poses a more urgent concern at the moment of service.