Ah, thanks for clarifying my understanding of the "natural born citizen" rule. I was operating under this misconception due to the whole nonsensical birthplace drama around Obama's election, and I appreciate the nudge to read up on it.

It seems like I was operating under a false understanding of it, and I'll remember that for the future.

> Japan actually has much narrower restrictions on who can become head of state than the US does. It just doesn't combine that role with the head of government.

Sure, fine, you can only be the Emperor of Japan by blood, just like you can only be "The Queen" (as recognized by the UK, Canada, and Australia) by blood. It's a ceremonial role, and I don't think it impacts my overall point.

The US rules are not only complicated but they have changed over time, and the determination is usually based on the rules at the time you were born. If both parents are American, or you are born in the US, it is pretty straightforward and mostly always has been. If only one parent is American and you are born overseas, “natural-born” citizenship is not automatic and depends on other factors. Having a single American parent is not sufficient on its own to be a natural-born American under US law.

This is why it became a thing with Obama. If he was born in the US then it was unambiguous. If he was born outside the US then the aggregate circumstances of his birth had a legitimate potential, under the rules at the time, to deem him not “natural-born”. It isn’t terribly surprising that people with a political angle were going to litigate that in the court of public opinion, and the vast majority of Americans have no idea how those citizenship laws work.

> True, though there is no clear consensus on what the former means, it is clear it is narrower than the latter.

No the consensus is pretty clear and only gets muddied up when there are political reasons for trying to invalidate someone's presidential candidacy. To become a citizen involves going through a "naturalization" process. A natural-born citizen is anyone whose citizenship came by birth rather than through naturalization. There may have been some ambiguity when the Republic was young, borders were porous, and documentation to track births and deaths and such was scarce or easily forged. But today we've got that all pretty much locked down.