A record of having been involved in terrorism, presented a threat to U.S. security, or been affiliated with other anti-humanitarian beliefs or groups can destroy a person's eligibility for a U.S. visa or green card (lawful permanent residence)—in other words, make the person "inadmissible." This can be a huge problem even for people who aren't themselves guilty of terrorism or other violations, but are simply viewed as having some connection to groups that do.
No matter what the basis of your potential eligibility for entry or residence—whether you have signed up for a tour, received a job offer from a U.S. employer, married a U.S. citizen, or won the diversity visa lottery—it will be worthless if you are found "inadmissible" under U.S. immigration law. This article summarizes the grounds of inadmissibility related to terrorism and other security issues.
(A separate but related category of inadmissibility has to do with crimes, as described in Crimes That Make U.S. Visa or Green Card Applicants Inadmissible.)
A full list of the grounds of inadmissibility can be viewed at Section 212(a) of the Immigration and Nationality Act (I.N.A.). They also include issues such as communicable diseases, past immigration violations, and the likelihood of relying on need-based government assistance.
A noncitizen will be found inadmissible to the U.S. if it appears that his or her reason for attempting to enter is to engage in legal violations relating to espionage, sabotage, prohibited export of goods, technology, or sensitive information, any other unlawful activity, or to oppose, control, or overthrow the U.S. government by force, violence, or other unlawful means. In other words, spies and saboteurs will never be given a U.S. visa (if the U.S. government knows about their background or intentions).
A noncitizen will be found inadmissible to the U.S. if he or she has virtually any sort of association with terrorism or a group that the U.S. considers terrorist, including if the person:
Check the statute for full definitions of terrorist activity, terrorist organization, and so on. In brief, terrorist activity is against the law where it was committed or would be unlawful in the U.S. and involves hijacking or sabotage; seizing, detaining, or threatening to kill or injure people in order to compel action by the governmental or some person; violent attacks upon an internationally protected persons; assassination; use of biological or chemical agents, nuclear weapons, or explosives, and so on.
This section of the law is so broad that it could sweep in people who are not actually terrorists. Let's say, for instance, that someone was forced to provide food to a local terrorist group as a condition for not torching their house. Would that person be inadmissible to the U.S.? It's quite possible.
In response, the U.S. government has said that it will make exceptions for people who were engaging in routine commercial or social transactions, providing humanitarian assistance, or were under substantial pressure, if such people can also satisfy a long list of criteria described in the Federal Register at FR Doc. 2014-02357.
If a noncitizen's entry to the U.S. would, in the opinion of the Secretary of State, have potentially serious adverse foreign policy consequences for the U.S., that person will be found inadmissible and denied a visa or green card.
Exceptions may be made for foreign government officials or candidates for foreign office or anyone whose beliefs, statements, or associations would be lawful within the United States.
Noncitizens who are or have been members of or affiliated with the Communist or any other totalitarian party (including subdivisions or affiliated organizations), whether domestic or foreign, will be found inadmissible and denied a visa or green card.
Exceptions may be made if the person became a member of the party involuntarily or force of law, or when below the age of 16, or in order to get a job, food rations, or other life essentials.
Another exception applies if the applicant for a visa or immigration benefit can prove that he or she is not a threat to U.S. security and the membership or affiliation ended at least two years ago, or five years ago if the party in question controlled the government.
Close family members who pose no threat may also qualify for exceptions in the discretion of the U.S. Attorney General, for humanitarian purposes, to assure family unity, or when it is otherwise in the U.S. public interest.
Noncitizens who, between March 23, 1933, and May 8, 1945, ordered, incited, assisted, or otherwise participated in persecution based on race, religion, national origin, or political opinion under the direction of or in association with the Nazi German government (including occupied areas and allies), will be found inadmissible.
Noncitizens who, outside the U.S., have committed, ordered, incited, assisted, or otherwise participated in the commission of torture or extrajudicial killing will be found inadmissible.
Noncitizens who have recruited or used child soldiers are inadmissible. Note that the child soldiers themselves will not be found inadmissible based on their position, though they could fall under one of the other bases of inadmissibility listed above.
For more detailed information on these grounds of inadmissibility, or to figure out whether one of the exceptions might help you qualify for a U.S. visa or green card, consult an experienced immigration attorney.