To dear jmh...
Even though it is illegal, many college students obtain and consume alcoholic beverages. If the police arrive on the scene (noisy party complaint?) the underage drinkers could be arrested for illegal possession of an alcoholic beverage, a misdemeanor generally carrying just a fine.
As to weddings: they are private parties for the most part in USA and I think there is something about "married persons" being legal adults but whether or not it applies to "drinking" I dunno.
For heaven's sake ... don't tell me there isn't there a Board contributor who has an attorney Mom or Dad?
Is there a lawyer in the house?
wow