From the transcript here:
"At the end of the day, the legal issue is quite straightforward, but I would note that the birther theories that Donald has been relying on -- some of the more extreme ones insist that you must not only be born on U.S. soil, but have two parents born on U.S. soil. Under that theory, not only would I be disqualified, Marco Rubio would be disqualified, Bobby Jindal would be disqualified and, interestingly enough, Donald J. Trump would be disqualified."
No one is arguing that to be eligible both parents must have been born on US soil, only that both parents must be citizens at the time of the candidate's birth in a US jurisdiction.
The extreme non-existent standard propounded by Cruz isn't necessary to exclude him, Rubio and Jindal (and Obama), only the constitutional one which defines natural born citizenship as beyond the reach of statute. Cruz' citizenship is statutory, not constitutional, and that is why he is excluded from eligibility. He acquired citizenship through the law, not through the Constitution:
'Because Cruz's citizenship comes from the law, not the Constitution, as late as 1934, he would not have had "any conceivable claim to United States citizenship. For more than a century and a half, no statute was of assistance. Maternal citizenship afforded no benefit" -- as the Supreme Court put it in Rogers v. Bellei (1971).
'That would make no sense if Cruz were a "natural born citizen" under the Constitution. But as the Bellei Court said: "Persons not born in the United States acquire citizenship by birth only as provided by Acts of Congress." (There's an exception for the children of ambassadors, but Cruz wasn't that.)'
