Repeated throughout the Wong decision is the implication that Wong's parents might have acted to renounce his citizenship during is minority...but did not.

Persons born on board a foreign naval vessel, even if in US waters or indeed if docked at a US port, are also an exception, not that I suppose this come up much. The Wong Kim Ark decision mentions this, but uses the now outdated term "public vessel".

@CosCallis that might have been possible in those days, but today it is not.

@DavidSiegel thanks for mentioning that; I had wondered what "public vessel" meant. By "naval vessel" do you mean mean specifically a military ship, as opposed to any ship of foreign registry or ownership? What about coast guard vessels? What about entirely nonmilitary government-owned vessels?

@phoog : As I read the mentions in the WKA decision, it would mean any military vessel. At that time most countries did not distinguish navy from coast guard. I am sure that it would not include non-government foreign ships, those would be "private", not "public". I am not sure about civilian government ships of other countries. I doubt there has been a case in US courts turning on that point.

Kenya is not one of these countries and does not allow dual-citizenship for adult citizens. They must renounce one of their two home countries upon reaching legal adulthood (I think 23.). This is where the Rumor's of Barak Obama's Kenyan Citizenship came from as he was in fact born a dual U.S.-Kenyan Citizen... However at the time of his Presidential Run in 2008, he had long ceased his Kenyan Citizenship. He was never not a U.S. Citizen though.

@hszmv not one of what countries? Countries whose laws operate automatically at birth? Do you mean that a child born in Kenya or of Kenyan parents must do something to assert Kenyan citizenship, or is that necessary only for dual citizens? (Also, there was no such thing as Kenyan citizenship when Obama was born in 1961, because Kenya was not yet independent. Obama was born a dual US/UK-and-colonies citizen.) (Further, according to Wikipedia, the Kenyan citizenship rules changed in 2010.)

Afaik unrestricted ius soli exists only in maybe 30 states, others do not have it, or have at least restrictions, like germany where depending on the circumstances you have to give up the other citizenship, and you can only apply it in the second generation. Additionally in basically all of these states you have ius sanguinis, and states like india have no form of ius soli at all. Note that given the US unique taxation problems a lot of international law institutions see the high barriers to renounce US citizenship as a break of international law.

The US is one of the few counties where being a citizen, even if you never enter the country can create real-life problem from the counties laws. (Due to the US tax system.)

"Most countries' citizenship laws ... operate this way for "normal" cases of acquisition of citizenship by virtue of the circumstances of birth.": no they don't. Jus soli "is the predominant rule in the Americas, but it is rare elsewhere", and is not practised at all in Europe.

@PlasmaHH Yes, I have also heard 30 or thereabout as the number of states with "unrestricted" jus soli. When I said "operate this way," I meant "operate automatically," whether the mechanism is jus soli or jus sanguinis. For example, the child of a Dutch citizen is automatically a Dutch citizen. I have edited the answer to clarify.

@SteveMelnikoff by "this way" I meant automatically. Jus sanguinis also operates automatically, in most cases, in the countries I know of. "Not practiced at all in Europe" is not correct. Many European countries have restricted jus soli. France, for example, has "double" jus soli, where anyone born in France of a parent born in France is French. Some European countries, at least, including the UK, also have jus soli that depends on the parents' immigration status. I am not aware of any country that has only pure jus soli or only pure jus sanguinis.

@phoog How about standing in line at an immigration checkpoint?

@axsvl77 Are you asking whether a child born before the mother has cleared the immigration checkpoint is a US citizen? The child would be a US citizen. This is true even for a child born in territorial waters, whose mother has never set foot on US soil.

@Phoog: The problem with Obama was rather unique, but basically, Kenya does not allow for Dual Citizenships. Anyone with Kenyan Citizenship from one parent and another citizenship from the other parent will need to either renounce the other citizenship if they can OR lose their Kenyan Citizenship automatically. As for your UK-and-Colonies thing, I am aware of that, but left it out for space concern. Essentially, when Kenya gained independence it's citizens (including Obama's Father) automatically had their UK citizenship changed into Kenyan Citizenship, and this Occured with POTUS.+

+Essenitally Barrak was born with US/UK citizenship initially... then it became US/Kenya when Kenya became independent, and then he did not renounce U.S. Citizenship, so automatically lost his Kenyan Citizenship. Under Kenyan Law, it is impossible to be both a Kenyan Citizen and a citizen of another country after a certain age so people in that situation need to make the choice or will lose Kenyan citizenship. As for the 2010 rule change, that would also be moot as in 2010 Obama was firmly just a U.S. citizen.+

+And this is not to say that Obama was ever disqualified to be POTUS as he was a birth to a U.S. Citizen anywhere in the world counts as Birth Right citizenship. In fact, John McCain, who was the opposition candidate for president in 2008 was also born out of the country (In Panama where his parents were stationed at the time of his birth).

@phoog: "France, for example, has "double" jus soli, where anyone born in France of a parent born in France is French". This is not exactly correct. Until 18 that person may ask (under conditions) to be French. At 18 it acquires French nationality only if it resides in France at that time and has been living in France for at least 5 years (accumulated) since he was 11 (source in French: service-public.fr/particuliers/vosdroits/F295)

@WoJ My statement was exactly correct. You perhaps overlooked the note on the page you link to that says it doesn't apply to children if one of the parents has also been born in France: "si l'un des 2 parents est étranger mais est né en France, l'enfant sera français de naissance"

@phoog: and you are right. I actually lost the "of a parent born in France" in your sentence - yes, the one I quoted :) My comment applies to just "someone born in France". Sorry.

@WoJ that's why they call it "double droit de sol": it applies to the second generation, while the page you linked to covers the first generation. I'm glad we cleared it up.

@hszmv, Kenya was not an independent country until several years after Obama's birth, so he could not have been a citizen of Kenya at birth — whereas he clearly was a citizen of the USA at birth due to both his birthplace (Hawaii, USA) and his mother's US citizenship and residence.

@DanLenski hszmv acknowledged the oversimplification of the facts in another comment, saying that Obama "was born with US/UK citizenship initially... then it became US/Kenya when Kenya became independent." It also appears that his mother hadn't lived in the US for enough years after her 14th birthday to pass US citizenship on to her son if he had been born outside of the US, because she wasn't yet 19 and the requirement was 5 years of residence.