Why should it be illegal? Why should we rely on the government to regulate personal behaviour? Are we not responsible enough to make decisions for ourselves and our children?
The Legal Side
Legally, the child doesn't have any rights until the age of 18, those right are instead inherited from the parents. In a case like this the child is usually too young to decide such a thing for themselves, and it's up to the parents to decide.
The Moral Side
It's not really "fair" to snip your kid at birth right away, especially when they are so young and fragile, and don't know whats going on. Most parents get their kids snipped for "medical reasons" which include transmitting a loveual disease easier since it's more difficult to keep the area clean
The Logical Conclusion
Obviously circumcision shouldn't be illegal, because it's already a choice from the beginning. It's not like the doctors force you to circumcise your kids, otherwise this thread might actually make sense.