All aliens or foreign nationals who are applying for admission to the United States must be inspected by U.S. immigration officials pursuant to INA § 235(a)(3). Applicants for admission to the U.S. obviously have far less rights than U.S. citizens or most Lawful permanent residents (green card holders).
Surprisingly, U.S. immigration law puts some categories of aliens who are already here into the category of those seeking admission. This includes Parolees and aliens who have entered without having previously been inspected. This obviously includes those who simply crossed the border with either Mexico or Canada. Section 235(a)(1) of the INA holds that an alien present in the U.S. who has not been admitted or who arrives in the U.S. (whether or not at a designated port of arrival and including an alien who is brought to the U.S. after having been interdicted in international or U.S. waters) shall be deemed an applicant for admission.
Upon applying for admission to the U.S. an applicant might be required to give a statement under oath. The applicant may then be questioned as to any information immigration officials require in regard to the reasons for seeking admission to the U.S., including how long the applicant intendeds to stay and if the applicant intends to remain permanently or become a U.S. citizen, and whether there is any reason that the applicant should not be admitted.
The Attorney General of the United States may allow the applicant to withdraw their application for admission into the U.S. pursuant to INA § 235(a)(4). In some cases, the immigration official may order summary removal of the alien.
The alien has the burden to show that he or she has a credible fear of persecution. If they fail to meet this burden, the officer shall order the alien removed from the U.S. INA § 235(b)(1)(B)(iii)(I). A written record must be made of this decision. Application may be made for review to an Immigration Judge.
An arriving alien who is considered a stowaway is not allowed to apply for admission or to be admitted and must be ordered to be removed after inspection by an immigration officer unless the alien indicates an intention to apply for asylum or a fear of persecution. In such a situation, the official must refer the alien for an interview by an Asylum Officer under Section 235(B)(1)(B) of the INA. If it is determined that the alien has a credible fear of prosecution, they must be detained pending further review. If it is not found that their fear is credible, they will be order removed. Alies who arrive from Canada or Mexico may simply be brought back.