I wouldn't advise trying it either. I've read occasional stories of people who were deported from the ship into the hands of the police at various ports -- not a pretty situation.
Also, when you disembark from the ship, the customs agents do use dogs. All the luggage is lined up in rows so that their furry, 4-legged agents can walk between the suitcases to detect any unusual items. Not worth it in my estimation.