A child who is born to or adopted by U.S. citizen parents (or in some cases, to only one U.S. citizen parent) outside the U.S. may, depending on timing, automatically become a U.S. citizen. This is called "acquisition" of U.S. citizenship.
When this child marries and has children, those children might also acquire U.S. citizenship at birth, regardless of where they are born. In effect, that means if your grandparent is a U.S. citizen, you might also have a claim to U.S. citizenship, even if your parent was never aware of holding U.S. citizenship.
Before deciding whether someone is a U.S. citizen based on acquisition, you need to check on the law that was in effect on the date of the child's birth. The relevant laws have changed several times over the decades, and set different requirements for the passing on and retaining of citizenship.
Most iterations of these laws regarding acquisition of citizenship require that the parent, the child, or both have spent some time physically living in the United States (had "residence" there). Sometimes the residence needs to have been for a specified length of time (such as five years) and sometimes not.
When the law doesn't say exactly how long the residence period must have been, you can assume that even a brief time, such as a month, might be enough, depending on individual facts and circumstances. In some circumstances, time spent abroad working for the U.S government can also count as time spent in the United States for this purpose.
The key element is often not the amount of time spent in the U.S., but whether or not you can obtain sufficient evidence to convince U.S. Citizenship and Immigration Services (USCIS) or the U.S. State Department that the parent was physically present in the U.S. for the period of time required in your situation. However, if the laws applicable to you require only proof of "residence," the exact length of time isn't as important as showing that your parent was actually "residing" in the U.S. and not just visiting temporarily.
For example, let's say both your parents were born in Israel and are married, but acquired U.S. citizenship at birth through their parents (your grandparents). under current law, your parents would only need to show that either one of them "resided" in the U.S. before your birth. If one of your parents lived for six months in the U.S. with a relative and attended high school, that would likely be sufficient to show "residence." But if one of your parents went to summer camp for one month every year for four years, that would not likely be considered a "residence." Still, it would count towards any physical presence time required.
Below is a brief summary of the laws in effect during different time periods.
If you were born before 1934, the law originally said that only your U.S. citizen father (not mother) could pass citizenship on to you. The father must have resided in the U.S. at some time before the child's birth. The law didn't require any particular length of residence.
Once a child obtained U.S. citizenship at birth through a U.S. citizen father, there were no conditions to retaining it. These rules also applied to children born out of wedlock (born to unmarried parents), provided the U.S. citizen father had at some time legally legitimated the child (acknowledged paternal responsibility). U.S. citizenship was then acquired at the time of legitimation, without regard to the child's age. This law was challenged several times as discriminatory, with some courts holding that citizenship could also be passed by the mother to the children.
Congress finally addressed this issue in 1994 and amended the law retroactively, to provide that either parent could pass U.S. citizenship to children. So, if you were born before May 24, 1934, and either of your parents was a U.S. citizen, that citizenship might have been passed on to you.
Also, if either of your parents was born before May 24, 1934, they might have acquired U.S. citizenship from either of their parents, which they then passed on to you under laws in existence at a later date.
If you were born between May 25, 1934 and January 12, 1941, you acquired U.S. citizenship at birth if both your parents were U.S. citizens and at least one had resided in the U.S. prior to your birth. The law at this time placed no additional conditions on retaining U.S. citizenship acquired in this way.
You could also get U.S. citizenship if only one of your parents was a U.S. citizen, as long as that parent had a prior U.S. residence. If your U.S. citizenship came from only one parent, you too would have been required to reside in the U.S. for at least five years before your 18th birthday in order to keep the citizenship you got at birth. This requirement did not apply to children born out of wedlock to a U.S. citizen mother.
If you were born between January 13, 1941, and December 23, 1952, both your parents were U.S. citizens, and at least one parent had a prior residence in the U.S., you automatically acquired U.S. citizenship at birth, with no conditions to keeping it.
If only one parent was a U.S. citizen, that parent must have resided in the U.S. for at least ten years before your birth. At least five of those years must have been after that parent reached the age of 16.
With a parent thus qualified, you acquired U.S. citizenship at birth, but with conditions for keeping it. You typically must have resided in the U.S. for at least two years between the ages of 14 and 28. Alternatively, if your noncitizen parent naturalized before you turned 18 and you began living in the U.S. permanently before age 18, you could retain your U.S. citizenship.
As a result of a U.S. Supreme Court decision, if you were born after October 9, 1952, your parent still had to fulfill the residence requirement in order to pass citizenship on to you, but your own residence requirements for retaining U.S. citizenship were abolished—you need not have lived in the U.S. at all.
If your one U.S. citizen parent was your father and your birth was out of wedlock (took place while your parents weren't married), the same rules applied provided you were legally legitimated (your father acknowledged paternal responsibility) prior to your 21st birthday and you were unmarried at the time of legitimation. If you were born to an unmarried U.S. citizen mother, these retention rules did not apply.
If you were born and raised outside the U.S., you might have not known that you acquired U.S. citizenship at birth directly from your parents or through them, from your grandparents. You might have then lost your U.S. citizenship by failing to fulfill the requirements related to U.S. residency.
Still, there are numerous exceptions to the retention requirement, which could apply to your case. If you were born between 1934 and 1952 and cannot prove that you meet the retention requirement, you might be able to take an oath of allegiance and restore your U.S. citizenship. Contact a U.S. consulate or USCIS office for more information. The relevant statute is 8 U.S.C. § 1435(d)(1), I.N.A. § 324(d)(1).
If, at the time of your birth, both your parents were U.S. citizens, married, and at least one had a prior residence in the U.S., you automatically acquired U.S. citizenship with no other conditions for keeping it.
If your parents were married but only one parent was a U.S. citizen at the time of your birth, that parent must have been physically present in the U.S. for at least ten years before your birth, and at least five of those years must have been after your parent reached the age of 14.
If your one U.S. citizen parent is your father and your birth was out of wedlock (took place while your parents weren't married), the same rules apply, provided you were legally legitimated (your father acknowledged paternal responsibility) prior to your 21st birthday.
If you were born out of wedlock and your one U.S. citizen parent is your mother (or if your father was a U.S. citizen as well, but you were not legally legitimated), your mother will need proof that she has one year of continuous physical presence in the U.S. prior to your birth.
If at the time of your birth, both your parents were U.S. citizens, married, and at least one had a prior residence in the U.S., you automatically acquired U.S. citizenship with no other conditions for keeping it.
If your parents were married, but only one parent was a U.S. citizen at the time of your birth, that parent must have been physically present in the U.S. for at least five years before your birth, and at least two of those years must have been after your parent reached the age of 14.
If your one U.S. citizen parent is your father and your birth was out of wedlock (took place while your parents weren't married), the same rules apply, provided you were legally legitimated (your father acknowledged paternal responsibility) prior to your 18th birthday.
If you were born out of wedlock and your one U.S. citizen parent is your mother (or if your father was a U.S. citizen as well, but you were not legally legitimated), your mother will need proof that she has one year of continuous physical presence in the U.S. prior to your birth.
The rules for acquiring citizenship are the same as those above, but with one major difference. As the result of a U.S. Supreme Court case, children born out of wedlock to a U.S. citizen mother and an alien father can acquire citizenship if the mother can show five years of physical presence in the U.S. prior to the child's birth, two years being after the mother was 14. This is the same physical presence requirement that already applied to children born out of wedlock to U.S. citizen fathers.
The U.S. Child Citizenship Act of 2000 made great strides in providing U.S. citizenship rights for children who meet the immigration laws' definition of an adopted child. Adopted children who were under 18 years old (or not born yet) on February 27, 2001 can acquire citizenship from their U.S. parents as long as they meet certain requirements. In order to acquire citizenship, the child must:
If the adoption was finalized abroad, the child will be issued an IR-3 visa and will get U.S. citizenship on the day he or she enters the United States. If it was not finalized abroad, the child will be issued an IR-4 visa, which requires "readoption" once the child arrives in the United States. On the date of readoption, the child will become a U.S. citizen.
Internationally adopted children entering the U.S. on an IR-3 visa receive a Certificate of Citizenship within 45 days of entering the United States. (This system started January 20, 2004.) Otherwise, you must apply for a certificate of citizenship from U.S. Immigration and Naturalization Services (USCIS). For instructions, read Filling Out Form N-600, Application for Certificate of Citizenship.
Keep in mind that the Child Citizenship Act is not retroactive. Thus if you were born abroad and adopted by an American parent and were 18 years old or older on February 27, 2001, your parents must have applied to naturalize you before you turned 18 or you must apply for U.S. citizenship on your own if they did not do this.
To learn more about applying for naturalization, see Application Process for U.S. Citizenship Through Naturalization.
An experienced attorney can assist with the task of figuring out whether a child has acquired U.S. citizenship and in requesting proof from U.S. immigration authorities.