Buy Kinder Surprise candy eggs in places such as Canada, Mexico, England and Europe, but not in the United States as of 2015. They are illegal and may not even be imported. If bought online, the Kinder eggs, if found, won't make it past customs. If a buyer tries to bring the eggs into the United States, the eggs are confiscated and a heavy fine is likely. The problem is the toy inside the egg.
The ban on candy that has toys hidden inside goes back to the 1938 Food, Drug and Cosmetic Act. That is the official law, but there is the suggestion that certain candy companies supported and used the law to ban competitor's products from reaching the U.S. market.
The law states that a non-food object, in this case the toy, may not be placed inside a food item unless it can be seen from the outside. Kinder could change the design and leave a space between the two egg halves, but this negates the "surprise" aspect.
The law cites safety as the main concern. The toys are small and may cause choking, but the eggs are not intended for children under 3 years -- Kinder prints labels on the eggs stating this.
It is risky and illegal to try to bring Kinder Surprise eggs into the United States or order online when chances are the eggs won't make it to your home. If visiting a country outside the United States and the Kinder Surprise eggs are available, eat the chocolate before returning home, and bring back the toy.