It sounds crazy, as I don't think the government should put people in jail for what they feed their kids, but veganism can lead to nutritional deficiencies if people aren't careful. It is very important that people practicing veganism get all of the essential amino acids, vitamins, and minerals their body needs.
Unlike meat inclusive diets, vegans have to pair certain foods to ensure they're getting proper nutrients. Now I'm sure there are vegan parents who may know what they're doing, but many probably don't, and a nutritional deficiency may be on the horizon for their kid.
I personally do not think infants or small children should be on vegan or even vegetarian diets. Infants need fat to ensure proper neural development, so restricting it in infants or even young children would do more harm than good. Animals and milk are great sources of fat, so you are taking a risk in restricting these foods.