[edge919]

Congress only has the power to naturalize. This is defined by the Constitution. Natural-born citizenship is defined outside U.S. law and outside the Constitution. This is what the Supreme Court said very clearly in U.S. v. Wong Kim Ark:

In Minor v. Happersett, Chief Justice Waite, when construing, in behalf of the court, the very provision of the Fourteenth Amendment now in question, said: "The Constitution does not, in words, say who shall be natural-born citizens.""

[Kansas58]

Congress can and has changed citizenship rules, for those born on foreign soil, several times.http://en.wikipedia.org/wiki/United_States_nationality_law