Congress didn't do that. The Constitution gives Congress the power to write laws of naturalization. An obvious part of that is to define who doesn't need to be naturalized to be citizens, i.e. natural-born citizens.
This is why acts of Congress have NO BEARING ON THIS ISSUE.
Sure they do.
What did natural born mean when it was included in the Constitution.
That definition depended on who you were talking to. Some, like Vattel, believed citizenship of the parents was the prime deciding factor. Others, like Blackwell, believed it was place of birth that was the deciding factor. Since the Constitution didn't define the term then it was certainly within the province of the Congress to do so.
Gee, guess I was wrong.
I certainly don't think that your being wrong on this question determines if you are conservative or not. And neither should you.
Not even Vattel. The people that quote him on this are doing so selectively. Vattel wasn't saying how things should be, he was reporting how things were. And when he wrote the part all the birthers love to quote he was specifically writing about some European countries. He followed the comment by pointing out that it was different in England, which all that matters to us.