The one-per rule doesn't make sense if it is just in regard to underaged drinkers. Sure, a willing over-21 person can smuggle a whole beer to someone a no-drink wristband on the tight (if show is close to, over over, soldout) floor. But....the ID check at door--including a magnetic stripe scanner that could retain ID info or interact with a marketing or law enforcement or county database --makes it somewhat difficult for under-21 to get booze.
Yes, if there's-a-will-there's-a-way; the rule forbidding more than one drink is silly because it chops severely at liquor sales and satisfied customers while only barely attacking the issue of the underaged.
Anyone, btw, have comments on that ID-swiping device at the front door..... "100 % ID Check Mandatory"