Your Japanese parent would have had to have notified the Japanese government within 3 months of your birth for you to have actually retained citizenship (Article 12). If they missed that window, you can re-acquire Japanese citizenship if you live in Japan, and are under 17 years old.
If you’re under 20 and you have retained your Japanese citizenship, you’re okay with both citizenships. You will be required to declare (Article 14–16) your final citizenship and renounce any other citizenship you hold within 2 years of turning twenty. If you haven’t made a declaration already, the Minister of Justice will formally request that you choose.
As I understand it, failure to make a positive declaration for Japanese citizenship is seen as renouncing it. Using your non-Japanese passport to travel to or from Japan — or making any other use of the foreign citizenship to do something not available to normal Japanese citizens (JET Program participation, work visas, Japan Rail discount pass) — is regarded as an intention to renounce your Japanese citizenship.
The US has no problem with dual-citizenship in most cases, but the Japanese government is less flexible. I’m married to a Japanese woman, so this is going to be an issue for our kids. I doubt that Japan is going to budge at all on dual citizenship in the next twenty years or so.
I know lots of Westerners here with their Thai wives whose children are dual nationality from birth. They just go down to their embassy and register the birth, then the child is issued a passport. The US tolerates dual citizenship – especially, I believe, in the case of Israel. Thailand forbids dual citizenship among adults and requires a child to choose upon reaching the age of 18. However, there is no way to check, and I’ve never heard of a Thai giving up his or her other nationality at that age. They generally just keep it a secret, entering and exiting Thailand on their Thai passports.
That’s not really connected - to benefit from the Law of Return, you still have to move to Israel. It’s an accelerated immigration process, and it doesn’t apply to Jews living outside of Israel.
It’s like how at the turn of the 20th Century, the U.S. would basically grant immediate citizenship to anyone showing up at Ellis Island. That doesn’t mean that people around the world could claim U.S. citizenship.
There is one exception to this rule I think: Native American reservations are, for all intents and purposes, foreign nations. They have their own flag and governing structures etc. All people born on them are considered dual citizens of the Nation of <Tribe> and the United States and the US recognizes this, as far as my knowledge extends at least.
That’s not really the case any more. In 2004 Ireland tightened one of its laws (the one that granted citizenship at birth to anyone born on the island). The law that allows grandchildren of Irish citizens to become citizens is still in force, but these days that’s not out of a desire to get new citizens, more because of the country’s collective memory of forced emigration.
In the debates over the 2004 referendum a few people did point out the inherent contradiction in the argument, made by supporters of changing the law, that citizenship was a privilege that shouldn’t be conferred on just anyone whose mother manages to get here in time for their birth, with a rule that allows someone who’s never set foot here and whose parents have never set foot here to waltz into an Irish embassy in their own country and walk out with an Irish passport (OK it’s not quite that simple but YKWIM). But nobody really listened to them.
Well, fair enough, but that’s not really the same thing when we’re talking about citizenship. I mean, my friend J. was born in WV, educated in PA, lived most of her adult life in LA and CA, and now lives in NJ. Is she a “citizen” of all of those states? Since (as far as I know) all US states treat resident citizens of other states the same as their own citizens, is there any meaningful definition of “citizenship” in this way?
So I suppose the question should really have been “What foreign nation recognises individual US states as sovereign entities?”
I was born to Mexican parents in the US. I have both citizenships. I vote and pay taxes in both countries. So to answer the OP: Yes, you can have dual citizenship by sole virtue of a parent’s citizenry.
The reverse holds true. If a baby is born to American parents in Mexico then it has dual citizenship.
When I was going through the process of getting Irish citizenship (by virtue of marriage), I contacted the US embassy just to make sure I wasn’t stepping on any toes. I received basically the same information then, and that was over a decade ago. Because I didn’t go into the Irish process carrying a burning US flag over my shoulder while befouling pictures of Mom, Apple Pie, and Chevrolet, no-one gave a damn.
A friend of my daughter has quadruple citizenship - triple by birth. He was born in France to an Australian mother who had German parents and hence was a dual Australian/German citizen, so French through being born there, Australian through his mother, and also German through his mother (since he was born after 1975). He became a Canadian citizen as a young child when his mother was naturalized after immigrating here.
Our daughter is a dual citizen of Taiwan (from her mother) and the US (from me).
Since Japan (the country of residence) is not a jus soli country, she does not have Japanese citizenship.
She is registered as US citizen with the government, soshe leaves Japan with her US passport, but we have her enter and leave Taiwan as a Taiwanese, with her Taiwan passport.