Even if you are not the bartender making the drink the role you play when it comes to underage drinking is crucial. Take a door bouncer for instance. He may not directly be serving the alcoholic beverage but his ability to verify proper identification and prohibit persons under the age of 21 into an establish that serves alcohol makes him just as responsible as the bartender.
Most States, Counties and cities have laws in place that prohibit minors from being in places that sells alcohol. In particular, Nevada has a law that states if an employee allows a minor to remain in a place that serves alcohol, the employee can be fined up to $1,000 and given jail time. And that establishment could possibly have their liquor license suspended or revoked.