The Federal Food, Drug, and Cosmetic Act prohibits non-food items from being encased within confections, due to choking hazards. This means that Kinder Surprise, chocolate eggs containing tiny toys, are banned in the U.S. Carrying them across the border or importing them illegally could result in thousands of dollars in fines.
Fortunately, for fans of these forbidden chocolate eggs, the company unveiled Kinder Joy, a similar treat that is permitted in the U.S. since the candy and the toy are kept separate. While the chocolate candy isn't quite the same as it's international counterpart, the approximation is close enough for many fans.