They get their facts wrong in the first sentence. John McCain was not born in the Panama Canal Zone. He was born in the Republic of Panama.
Though it's a moot point right now, that seems to be debatable. I've seen McCain's birth certificate, and it is bilingual, with English ahead of Spanish, and was issued under the auspices of the "Panama Canal Commission," not under the auspices of the Republic of Panama. My take is that the hospital in which he was born was United States property and under the jurisdiction of the US Navy.
It's amazing that this law review article kicks around the constitutional eligibility question for McCain and neglects Obama's much more tenuous constitutional eligibility status. But then again, I'm sure you're aware of the political biases of most legal academicians.
If you haven't seen this, it makes for interesting reading; particularly 7 FAM 1110 through 1140.