If citizenship IS designated by statute, then we should be able to take care of the birthright citizenship question statutorily. That is basically what the 1898 birthright citizenship Supreme Court ruling says: that in the absence of a Congressional statute, all born on American soil are citizens. Congress could have fixed this more than 100 years ago, and certainly within the past 20 years or so when the problem became so evident.
The only citizenship that is designated by statute is the citizenship of alien immigrants, their children & of course the dreadful citizenship given to babies born here to illegal aliens. Children born to 2 citizen parents are natural born, their citizenship can not be taken away without leaving them stateless, unlike children born to aliens, legal or illegal, who have a foreign allegiance to fall back on. These children can never be left stateless, therfore they are not natural born and they are not citizens for Article II constitutional purposes.