Its actually not illegal....kind of

The actual law for selling drinks to someone who is already intoxicated applies to pubs, bars, restaurants. It specifilcally calls for "serving" someone who is intoxicated a drink. Selling unopened liquer to someone from a store who is drunk is a grey area and in very hazy grounds when it comes to the law because you are not serving them the drink to drink there, they are "buying" the alcohol to comsume at an unknown time.

most states law gives the bartender or clerk the responsibility to cut a person off when they feel the person is "too drunk". So its easy enough to say, he looked ok to me. There is no set rule. Plus some people can look extreemly drunk (Im looking at you Jim Bruer) and some can look extreemly sober while being extreemly drunk.