[WOSG]

You have it almost but not quite right. Congress' powers to specify and to elucidate the exact boundaries of this "under the jurisdiction" clause are in the 14th amendment itself:

"Section 5. The Congress shall have power to enforce, by appropriate legislation, the provisions of this article."

[inquest]

Maybe I should put my question in a different way: Does Congress have the power to deny citizenship to anyone who's had every honest reason to think of himself as a citizen his entire life? Myself or yourself, for example?

If not, how is the line drawn?