Originally Posted by
HereAndThereSC
That is correct, but the application of the law by customs will be at their discretion. I've been camping numerous times between 18 and 21 years of age from Montreal to upstate NY, often we brought beer into the US by land. Sometimes we'd be asked if we had any beer/etc, we would always answer honestly. We never got any confiscated, and we were usually told "just be good and don't drive if you drink". "Yes sir!".
HTSC
Yeah, wait a second. US Immigration is a federal agency, and the drinking ages are mandated by state law. I guess they wouldn't have the jurisdiction to stop that.