I am a French citizen living in the US for many years with a green card. I am looking to obtain my US citizenship. Will I loose my French citizenship or can I keep dual nationalities?
Generally speaking, French law does not make multiple citizenship difficult in any way. You don't need to renounce any prior nationality to become French and there are very few situations in which you lose it when you are. Perd-on la nationalité française en acquérant une autre nationalité ? is a brief overview of the latter aspect from the official vosdroits.service-public.fr website.
For a long time France was a party to the 1963 Strasbourg convention, which did provide for the loss of one's first citizenship when acquiring that of another party to the convention. But it had some exceptions and the US was never part of it (it was strictly a European thing). Since then, France denounced the relevant chapter of the Strasbourg convention so that all this is only of historical interest.
I don't really know about the US end of things but I assume it should be OK too as the US tends to be permissive in this respect and there are many dual US-something citizens.
According to Wikipedia on French nationality law:
Dual citizenship has been permitted since 1973. Possession of one or more other nationalities, does not, in principle, affect the French nationality.
(I'm afraid I don't have an official reference for that.) For the US side, acquiring US citizenship does not require that you give up other citizenships. I have a Dutch friend who obtained US citizenship by naturalization and continues to hold both citizenships. It can, however, get somewhat more complicated to comply with the taxation regulations of both countries of citizenship.
1In the OP's case, taxes should not be an issue. He is already a US resident and France does not care in the least about citizenship when it comes to taxes. Only difference is that he would still have to deal with the complexities of the US rules should he leave the country for good.– GalaApr 29, 2015 at 23:59
If "many" years he had green card amount to 8 years or more, then it doesn't matter in the US as well. With regards to taxes, green-card holder who gives up the green card after 8 years or more is treated exactly like a citizen renouncing citizenship. Apr 30, 2015 at 3:47
1By becoming a US citizen, someone is never free of the US IRS short of renouncing that citizenship. I don't know anything about Mimi's future plans but that's a significant consideration for a permanent resident who might want to retire back in their original country. AFAIK, the US is the only country in the world that makes its citizens living elsewhere file a tax return and potentially pay taxes.– tetranzApr 30, 2015 at 17:16
@tetranz as I said, the US treats former permanent residents who were green card holders for 8 years or more the same as former citizens. May 1, 2015 at 0:20
1Yes, I think you're talking about expatriation tax. My point is that it's a lot easier to become a former permanent resident than it is to renounce citizenship. If a green card holder leaves, they are fairly quickly free of US tax obligations. I'm just suggesting that it might be one more thing for a green card holder to think about if they're weighing up the pros and cons of becoming a citizen if they might one day permanently return to their original home country.– tetranzMay 1, 2015 at 1:58
The answer is unequivocally: "NO". You can have as many citizenships as you wish as long as you comply with entry exit passport-rules of each respective country. Example: If you become US citizen you can no longer enter US as French national using French passport.
2To clarify: you're speaking from the perspective of France, correct?– Dan GetzAug 3, 2015 at 11:45
The US Immigration Oath that one must make at the time one is sworn in requires one to "renounce and abjure" all previous nationalities and titles of nobility.
Whether the government of your previous nationality would be informed of this action or recognises US naturalisation as an explicit renunciation would need to be cleared with them.
1It's well-known but does it really mean you have to renounce any prior citizenship? I could not find any requirement to show that you did and I vaguely recall that this part of the oath of allegiance referred to service in a foreign military or things like that.– GalaApr 30, 2015 at 9:28
3What this means in practice is that by swearing that oath, one agrees that the US government will not treat a dual national as a citizen of any other country, but only as a US citizen. There are a great many naturalized US citizens who also still hold other citizenships. Apr 30, 2015 at 20:17
3"requires one to "renounce and abjure" all previous nationalities and titles of nobility." Nope. The oath does not mention "nationality" at all. And in any case whether you have a country's nationality is solely determined by that country's laws. May 1, 2015 at 0:34
@user102008 true, but its wording is of the type that would make a person wonder. This answer only amounts to recognizing that a question was asked. Maybe it should have been a comment.– Dan GetzAug 3, 2015 at 11:52