For the protection of the U.S., people with histories of criminal or terrorist activities, drug abuse, infectious medical problems, or certain other characteristics will never be allowed a visa, green card, or U.S. entry, unless special permission is granted first. In immigration law terms, these characteristics are known as the grounds of inadmissibility. (See Section 212 of the Immigration and Nationality Act, or I.N.A..)
Following is a short, summary list of the major categories of inadmissibility. It includes a description of whether there's a chance of applying for a waiver, which forgives or overlooks the inadmissibility problem in your case.
|Classes of Inadmissibility||Waivers Available?|
|People with communicable diseases of public health significance, such as tuberculosis||Yes|
People with physical or mental disorders that
|Drug abusers or addicts||No|
|People without proper vaccinations||Yes|
|People with convictions for crimes involving moral turpitude||Yes|
|People who have violated immigration laws||Yes|
|People with multiple criminal convictions||Yes|
|People likely to become "public charges," dependent on need-based government assistance
For details on immigration violations that can make you inadmissible, see Consequences of Unlawful Presence in the U.S.: Three- and Ten-Year Time Bars, and The Permanent Bar to Immigration for Certain Repeat Violators. For details on criminal violations that can make you inadmissible, see Crimes That Make U.S. Visa or Green Card Applicants Inadmissible. Also see Who Is Barred From the U.S. as a Terrorist, Spy, or for Other Security Reasons.
Everyone who applies for "admission" to the U.S. is checked to see whether he or she is inadmissible. However, not every type of applicant is subject to every ground of inadmissibility. For example, VAWA applicants are exempt from such grounds as public charge and unlawful entry. Asylum-based and refugee applicants are similarly exempt from such grounds.
Although the word “admissibility” sounds like it applies only to someone who is outside the U.S. applying to get in, for immigration purposes, it also applies to people who are already in the U.S. applying for a different status, like permanent residency. They too must be “admissible.” The law treats them like they’re outside the U.S. asking to be let in, even though they’re already inside the United States.
Also, it doesn't have to be a newcomer, seeking their first entry. Even someone who already has a green card will, if they spend 180 continuous days or more outside the U.S., left during removal proceedings, or committed a crime, be questioned by U.S. border officials, and their records checked, to see whether they've become inadmissible. (See I.N.A. § 101(a)(13)(C).)
If you hold a green card, one way to avoid this problem is to apply for U.S. citizenship as soon as you're eligible. For more information, see Becoming a U.S. Citizen: A Guide to the Law, Exam, and Interview, by Ilona Bray (Nolo).
The various agencies handling your immigration-related applications may decide you are inadmissible any time you ask for permission to enter or stay in the United States. These agencies include the U.S. State Department and the Department of Homeland Security, through its subagencies Customs and Border Protection (CBP) and U.S. Citizenship and Immigration Services (USCIS, formerly the Immigration and Naturalization Service, or INS).
These agencies can use your inadmissibility to block you any time you try to cross the border, apply for a green card, or apply for any other type of visa or immigration status. If you're at a U.S. border when this occurs, you could be turned around and sent home, or be sent to immigration court for removal from the United States. If you're in the U.S., you also might be put into removal proceedings.
Even if you fall into one of the categories of inadmissibility, you might not be absolutely barred from getting a green card or otherwise entering the United States. You might be able to get around the problem, if, for example, your illness can be cured or the doctor diagnosed you wrong, or the U.S. government made a mistake in your case and you aren't really inadmissible. If none of these work, you might be able to apply for a waiver, meaning you ask the U.S. immigration authorities to overlook the problem and admit you anyway.
There are many technical factors that control whether you can overcome a finding of inadmissibility. For more on the grounds of inadmissibility and how to overcome them, see the book U.S. Immigration Made Easy, by Ilona Bray (Nolo). Or if you're applying for a green card, get a quick overview of the possibilities in the article When Is a Waiver of Inadmissibility Available to a Green Card Applicant?
You might ultimately need to hire a good immigration lawyer—see Nolo's Lawyer Directory to find one in your geographical area with experience in this area of immigration law.