Then who had the authority to define it and where is it defined?
There was an understanding of the term at the time. The issue rarely comes up, and it's been so long, it's hard to put one's finger on exactly what that understanding was.
Who's understanding would that be?
That's why we have courts, to enforce contracts, and punish criminals. Now if the courts, including the Supreme Court would just do their job and determine what the definition was for Constitutional purposes, we'd be fine. But instead they are dancing around trying hard to not decide.
They have, 110 years ago. In the Kim case.
If Congress can redefine the Constitution, we in effect have no written Constitution, just a living breathing document that can mean whatever it's expedient for it to mean.
That is a ridiculous statement. For the Congress to redefine the Constitution in this matter then the Constitution would have to define what natural born citizen was. The Constitution did not. What it did to was give Congress the authority to establish naturalization laws. Part of that process, by definition, has to be defining natural born citizen. That that they have done. By defining citizen at birth and establishing the fact that there are two classes of citizen, not three.
Who defined "arms" in the second amendment? It was just understood. But historicial digging can reveal what that understanding was.
They have, 110 years ago. In the Kim case.
Was Kim a candidate for President? Did the decision use the term "natural born"?
A quick look at the decision, says no. Definitely to the first question, and in the final decision, as opposed to the analysis, also no. They declared Mr. Kim to be a Citizen, and implied that he was natural born, by viture of his being born in the US. But they also say that it's because of the 14th amendment, not any ordinary law Congress passed. thus the case does not address the situation of McCain, nor of Obama if he were born abroad.
Under that decision, Mr. Obama would be a natural born citizen if born in the US, regardless of the citizenship of his parents.
The evident intention, and the necessary effect, of the submission of this case to the decision of the court upon the facts agreed by the parties, were to present for determination the single question, stated at the beginning of this opinion, namely, whether a child born in the United States, of parents of Chinese descent, who, at the time of his birth, are subjects of the emperor of China, but have a permanent domicile and residence in the United States, and are there carrying on business, and are not employed in any diplomatic or official capacity under the emperor of China, becomes at the time of his birth a citizen of the United States. For the reasons above stated, this court is of opinion that the question must be answered in the affirmative.