It's never happened to me personally, but I know loads of people who have had booze confiscated at various points of entry by customs officials because they are not 21 and trying to bring alcohol into the U.S. You can sneak it through or even mail it to yourself -- if you did something like FedEx overnight in a styrofoam wine container, you could feel pretty confident that it would arrive intact. It might save you some worry but add to another -- how badly FedEx would treat the bottle. If it's good stuff, I'd just try to get it through myself.