The Panama Canal Zone was under US administration when McCain was born, and he was on a US Naval base, so in some sense he was in US territory.

The more interesting story is that of Ted Cruz, who had a noncitizen father and was born in Canada.

"In some sense" is what gets interesting :-) But I agree that both fall into an interesting (if probably not ultimately very important) area of ambiguity in US constitutional law and common law.

Not so ambiguous. Born on a US military base counts as US soil.

No it is not:

https://travel.state.gov/content/travel/en/records-and-authe...

The arguments as I recall were basically two-fold: 1.) At the time, it was the Canal Zone (which wasn't quite US soil but maybe close enough) and 2.) There were some long-standing common law precedents related to agents of the king, diplomats, etc.

US law has traditionally held that if both parents are US citizens then the child is a natural-born US citizen regardless of where in the world they are born. This was specifically in support of diplomats, military, etc. I am not aware of a context in which this wasn’t true.

The only complicated area in law is when only a single parent is a US citizen and the child is born overseas. This was a consequence of the 20th century reality that the US had vast numbers of military personnel stationed globally.

If either of your biological parents is an American citizen, you are automatically a natural born American citizen, regardless of where geographically you are born.

This is why Obama, McCain and Ted Cruz are eligible for the Presidency

edit: doh. Forgot that Obama was born in Hawaii