As mentioned above, there are two ways for a person to become a US citizen. The first is by operation of law where no specific act by the individual is required. This would include birth in the US, or birth abroad to US citizens or nationals. The second way is by naturalization.

The 14th Amendment to the United States Constitution provides that all persons born in the United States and subject to United States jurisdiction shall be citizens at birth. What is important is where the child is born, not the citizenship or residence status of the parents. Thus, a child born in the United States of illegal alien parents is still a United States citizen at birth. The only exception is that the child must be subject to the jurisdiction of the United States. Therefore, a child born to certain foreign diplomats or sovereigns are not US citizens at birth, since they are born while their parents are not subject to the jurisdiction of the United States since they are in the US as representatives of foreign governments.

There are also many instances when a child born outside of the United States is considered a citizen at birth. For instance, if a child is born in an outlying possession of the United States (which includes American Samoa and Swains Island), or in a US territory, such as Puerto Rico, Guam, the US Virgin Islands, etc., they may be considered US citizens at birth.

To determine whether a child born outside of the United States is considered a citizen at birth, you must look to the appropriate statute and to the citizenship status of the child's parents at the time of the child's birth.

Furthermore, the law on acquisition of United States citizenship at birth has changed numerous times over the years, most recently with the Child Citizenship Act of 2000, which became law on October 30, 2000. Under this act, any foreign-born child under the age of 18 who has one citizen parent, resides in the custody of that citizen parent, and is residing in the US as a permanent resident automatically becomes a citizen. The law applies to both natural and adopted children. The law also allows citizen parents to petition for the naturalization of non-citizen children who do not reside in the US.

What about dual citizenship? This arises when a person is considered a citizen of two or more countries at the same time. The United States does not favor the concept of dual citizenship and, in fact, when a person is naturalized in the United States, they are required to renounce any and all other citizenships which they may have. However, there are situations when a US citizen can also be a citizen of another country. This usually occurs in cases where the foreign country does not require its nationals to renounce its citizenship when that person is naturalized in the United States, or where a person is born in the United States of parents who are nationals of other countries, which base their citizenship on parentage. Thus, in such a case, the person is a citizen of the United States by birth in this country, and a citizen of the foreign country by virtue of the nationality of the child's parents.

As mentioned above, the second method to obtain US citizenship is through naturalization. In order to be naturalized, the first requirement is that the applicant be a lawful permanent resident of the United States. An exception exists for those who served honorably in the US armed forces in times of war. The second requirement is that the applicant must be at least 18 years of age at the time of filing the application for naturalization. Again there is an exception for those who served honorably in the US military during times of war, as well as for minors who have at least one US citizen parent who petitions for them.

The next prerequisite is that the applicant must have satisfied certain residency requirements. Initially, the applicant must have been physically present in the US for at least half of the required residence time preceding the date of filing the application. The statutory residence time is five years, unless naturalization is based on marriage to a US citizen in which case it is only three years. (In this situation, the alien must have been a resident for at least three years and must have been married to, and living with, the US citizen spouse for at least three years.) A person is permitted to file their application for naturalization three months prior to meeting the physical presence requirement.

In addition to the above, an applicant must not have abandoned their physical presence in the United States. If a person remains outside the United States for one year or more, then they have broken their continuous residence for naturalization purposes. It does not matter that the person had permission to be outside of the US, such as with a US re-entry permit. The only exceptions are for those serving in the US armed forces, with certain US government agencies, as religious workers, or with certain international groups. In these cases, the applicant must have filed an application to preserve residence for naturalization on US immigration form N-470. This application can only be approved if the person had been physically present in the US, as a permanent resident, for at least one year, prior to filing the application, and it must be filed before the person has spent one year abroad. If the applicant is absent for more than six (6) months, but less than one (1) year, there is a rebuttable presumption of abandonment of continuous residence for naturalization purposes.

The alien would have to show that he or she did not intend to abandon their permanent residence and that there were valid reasons for their extended periods outside of the US. If the absence is six months or less, then there is no break in the continuous residence requirement.

Also, the applicant must reside within the state or within the US immigration district where the application will be filed for at least three months immediately preceding the filing of the application.

In addition to the residence requirements, the applicant must also be a person of good moral character during the statutory period (3 or 5 years), and it must continue from the time of filing the application through the swearing-in ceremony. The term "good moral character" is not specifically defined in the US immigration Act; however, the courts have interpreted it to mean behavior that measures up to the standards of the average members of the community. The US immigration Act, in section 101 (f), does list certain offenses that would preclude an applicant from establishing good moral character. These would include such crimes as murder, aggravated felonies (which are more fully described in the section under deportation grounds), certain gambling and drunk-driving offenses, prostitution offenses, etc. An applicant may also be found not to be a person of good moral character if he or she willfully failed to support dependents, committed adultery, which destroyed a viable marriage, or willfully and knowingly failed to register with the Selective Service, if required to do so.

An applicant must also be attached to the principals of the Constitution and be favorably disposed to the good order and happiness of the United States.

Therefore, an applicant for naturalization must take the full oath or affirmation of allegiance to the United States, without any mental reservation.

A person may take a modified oath provided his or her reason for doing so is due to deeply held religious or moral beliefs, which limit his or her willingness to bear arms and/or perform noncombatant services in the US armed forces.

Certain classes of persons are barred from naturalization. These include subversives; deserters from the US armed forces; those with a pending or final order of deportation (an exception exists for those who served honorably in the US armed forces for a period of three years or during times of war); and aliens who applied for and received an exemption or discharge from training or service in the US armed forces.

Applicants for naturalization must also be able to read, write, and speak the English language. Persons who are physically unable to comply due to a permanent physical or developmental disability, or permanent mental impairment are exempt from the literacy requirements. In addition, applicants who are more than 50 years of age and have been permanent residents of the United States for more than 20 years, or are more than 55 years of age and have been permanent residents of the United States for more than 15 years, as of the date of filing the application, may be examined in their native language rather than English.

All applicants are required to pass an oral test on the history and government of the United States. From a standardized list of approximately ninety-five (95) questions, ten (10) questions are asked, and the applicant must answer at least six (6) correctly.

To obtain naturalization, an applicant must file US immigration form N-400, together with supporting documentation, including photographs, and evidence of lawful permanent residence, with the US immigration regional service center office having jurisdiction over the place of the applicant's residence in the United States. The appropriate filing fee must accompany the application, together with a separate fingerprinting fee. As stated previously, the application may be filed up to three months before the applicant meets the residency requirements.

The application is then processed by the regional service center. The applicant will be scheduled to have fingerprints taken at an US immigration-fingerprinting center. The fingerprints are then forwarded to the FBI for background checks, while the US immigration service requests the original alien file of the applicant. When the fingerprint checks have cleared and the original file is located, the applicant is scheduled for an interview at the US immigration office located closest to his or her place of residence in the United States. The processing time can take anywhere from six months to one year or more depending on the caseload of the individual US immigration office.

At the naturalization interview, an US immigration examiner will review the application with the applicant for completeness and correctness, and will test the applicant on his or her knowledge of US government and history, as well as their ability to speak, read, and write the English language. The examiner will also determine whether the applicant meets all of the requirements for physical presence and good moral character, and if they are otherwise eligible to be naturalized. An applicant who fails the exam may request to be re-tested within 90 days of the first interview.

If the applicant passes the examination, and is otherwise qualified, the application will be approved and the applicant will be scheduled for his or her swearing-in ceremony. If the examiner is unable to make a decision on the application during the initial interview, the applicant will be scheduled for a follow-up interview, which must be scheduled within 120 days. If the examiner denies the application, either during the initial or second interview, a written decision will be issued and the applicant will have 30 days in which to file an appeal. Another US immigration examiner within the same office will review the case. The US immigration service must make a decision on the appeal within 180 days. Usually the applicant will be re-interviewed and given the opportunity to present any other evidence to support his or her case. If the application is again denied, or if no decision is issued within the 180 days, the applicant may seek review in the federal district court. The US immigration service may also deny the applications of those who fail to attend their swearing-in ceremonies.

Persons who are sworn in as US citizens are immediately eligible to enjoy all of the benefits of citizenship, including the right to apply for a US passport, the right to vote in federal and state elections, the right to petition for family members to join them in the United States, the right to serve on juries, the right to receive federal assistance, and the right to apply for most federal jobs.