In my former occupation I had to deal with this myself quite a bit. Our Golf Course sold considerable amounts of beer, especially on weekends. the TABC (Texas Alcoholic Beverage Commission) policy was that you had employ the '10 year rule' where you carded anyone who 'looked' like they were within 10 year window of the legal drinking age in Texas (21). We were inspected about once every 2 or 3 years by a uniformed member of the commission you quizzed the employee on duty and checked our displayed permit, notices and paperwork.. Now a grocery or convenience store likely was checked every year if not more often. A couple of times I had to wade thru the regs and they were Byzantine depending upon what kind of venue you were.