Assume a woman marries a foreign man for the purposes of him gaining citizenship. They stay married for a few years but never actually develop a real romantic relationship and by this point the woman has met another man she truly wants to marry for love. If she and this man get divorced so she can legally marry the man she actually loves would this affect the citizenship of the former green card husband? Or would he remain a citizen without any issue?
Naturalization obtained by fraud or misrepresentation, including misrepresentation in earlier applications for immigration benefits, can be revoked. This requires action on the part of the US government. The divorce would have no automatic effect on the citizenship of the naturalized spouse.
Assuming that the naturalized spouse had obtained lawful permanent residence (i.e., a green card) by virtue of a petition based on the marriage, the naturalized spouse could be denaturalized if US Citizenship and Immigration Services (USCIS) came to believe, and to be able to prove in court, that the marriage had not been genuine. This would be true even if the couple had not divorced.
The only effect of the divorce, therefore, is that it could increase the likelihood of USCIS becoming aware of the true nature of the marriage. There is no direct effect.
We don't have "green cards" here, but I am assuming a "family reunion" visa, with your partner being a citizen married to you.
When you apply for that, you first get a temporary residence permit. This can be revoked, or simply not extended, based on conditions such as your marital status or "normal" crimes committed here. For example, getting caught with drugs might endanger that status.
If you still meet the conditions for family reunion, after a while (a few years: it depends on many things, let's just say it's somewhere between 3 and 5) your temporary residence permit runs out and you can apply for a permanent one. This can still be revoked later, but now we are talking about heavy stuff. Crimes against the constitution. Armed insurrection. Joining a foreign enemy army. Terrorism. Things that will land you in jail for a decade anyway. Normally, "permanent" actually means permanent, even if your marriage ends or you commit a "normal" crime. I think the actual plastic card expires every ten years, but there are no conditions on renewing it. Just bring the old one and your passport.
Again after a while (again, between 3 and 8 years depending on many factors: previous citizenship, marital status, language skills etc), you can apply for citizenship. Citizenship can never be revoked if you drop your original citizenship. Germany only revokes citizenship in very serious cases and only if the perpetrator had multiple citizenships to begin with. We are talking international incident level serious.
So a normal divorce has no effect once you have reached the "permanent" status and marriage is no longer a condition needed. Assuming the marriage was real in the first place. I don't think anybody would look twice if you got divorced after lets say 7 years - 3 years after your permanent residence permit. Life happens and it's not always pretty.
Now if you threw a party and got happily divorced the day after your permanent residence permit arrived in the mail, the authorities might check for fraud. And if they consider your marriage fraud, then it doesn't matter where in the process you are really. Citizenship built on fraud can be revoked up to ten years after you got it, even if it means you will then be stateless.
The timeframe for the procureur de la république to revoke a naturalization through marriage (Nationalité par déclaration, which you can apply to after 4 years of marriage) is 2 years of the date of the acceptance of the declaration
Any separation/divorce in the 12-month period following the acceptance of the declaration will automatically be treated as a suspicion of fraud and can lead to the newly-French having their citizenship revoked after an investigation and a favorable opinion by the Conseil d'état (the highest administrative court)
If the citizenship is sought through naturalization (Having lived 5+ years in France, having fought for the Foreign Legion...) instead of marriage, the divorce would likely not impact the proceeding (though the timeframe is the same)
After those 2 years, it is impossible for the citizenship to revoked unless, in the following 10 (or 15) years after acceptance of French nationality (a French national from origin can't be stripped of their nationality this way), and provided the holder has another citizenship, are committed :
- Crimes et délits portant atteinte aux intérêts fondamentaux de la Nation (as listed in Book IV, title I of the Code pénal
- Acts of terrorism
- Crimes and delits, committed in a public capacity, against the administration itself (Book IV, Title III, Chapter II)
- Haven't fulfilled the obligations of the national service (Census (between 16 and 25yo), eventual military service...)
- Acts for a foreign nation that isn't compatible with holding French citizenship