Description of somebody, usually in their late adolescence, who looks significantly younger than their actual age, and in turn, upon suspicion of being underage, will be checked for ID for (jokingly) the rest of their lives.
Dave: You're telling me that kid is in grade 12? Or did you say that he is 12? It sure looks so.
Michael: Yea, he'll be carded for life.
Describing someone who is too young and feeble to be of any use to society, and instead is a burden. Can also describe the sellout children who are undercover cops who try to nail stores for selling cigarettes to them. Implies that the person in question is so young and infantile that they aren't even old enough to buy a pacifier to suck on.
Yooou watch Yu-gi-oh?! You probably get carded for buying a pacifier!
The little boy who came to the SuperFresh to try and buy a pack of Camels is so young, he should be carded for buying a pacifier.
Little Johnny drops a duece in his parents bed, and would be carded for buying a pacifier.