Nobody in his right mind would doubt that Sen. John McCain is an authentic American. He is undoubtedly a citizen of the United States and many would say that he is something more: an American hero who was held prisoner in Vietnam.

But there's one thing that he is not: Unlike everybody else who has taken the presidential oath of office, he was not born in any of the 50 states. He was born on a military base in the Panama Canal Zone.

That's a theoretical legal problem. The Constitution says that only a "natural-born citizen" can be president, which has long been understood to mean that only those born in this country can be president. Nobody thinks, for example, that the Austrian-born governor of California, Arnold Schwarzenegger, qualifies.

But what does "natural-born" really mean? Like some other words in the Constitution -- cruel and unusual punishment, well-regulated militia-- its meaning was not defined back in 1787 and has been the subject of much debate since.

As The New York Times reported last week, in a story about the legal ramifications of the question and the stirrings about it, the meaning of natural-born "has never been definitively resolved by either Congress or the Supreme Court."

Mr. McCain is not the first to have a small asterisk attached to his candidacy. Republican Barry Goldwater was born in the Arizona territory in 1909, three years before it became a state. (The same question could have been raised had Barack Obama, born in 1961, come into the world just two years earlier when Hawaii was not yet a state.)

Of course, as a matter of common sense, Mr. Goldwater was natural-born. So is Mr. McCain because a military base, a U.S. warship or an embassy is a sovereign extension of the United States -- the flag flies over it and U.S. law governs all who serve on it. Despite phony concerns about activist judges making up the law, the legal opinion of any court would reflect this common sense. To do otherwise would be to tell American servicemen and -women that their children born overseas are second-class citizens.

As controversies go, this is a nonstarter, but a delicious irony attends it. Until set straight by the Supreme Court, the Bush administration made the ludicrous legal argument that the U.S. base at Guantanamo Bay was out of reach of federal courts because it was really the property of Cuba.

If the administration had prevailed in that argument, Republicans might really have something to worry about, because it would be hard to argue that one U.S. base could be a Constitution-free zone to house terror suspects but another was a U.S. sovereign territory for the purpose of birthing potential presidents. For a natural-born argument, it would have been downright unnatural.