The items held within the vagina do not necessarily have to be illegal, one may well stash spare change or chapstick there.
T: "I think I have a crush on J's mom."
K: "J's mom has too many STDs. She's cuntraband."
T: "Would you ever sleep with L?"
K: "Nah...S has had his way with L. You don't want to mess with him. L is cuntraband."