Back when I was still being trained as a cashier I was rather nervous about carding people for alcohol. I'd card people I know looked old enought to purchase it, but I figured I'd flatter them, yanno? Yeah, I don't do that anymore. First complaint came from an older woman who complained to a manager about my carding her. Second complaint came from a man who went straight to the store director to complain. Not about the fact that he was old enough, but about the fact that he was an undercover cop and couldn't be carded. Thankfully, one of the Service Coordinators was walking by and took over for me, because he was incredibly irate, and told him I was only doing my job. Apparently he was good friends with the store director, who in the end just told him that I was doing my job too. He stormed off after paying, and the SC told me he was just BSing and that everyone you ask for an ID for has to show you it, regardless of their occupation.