The Controlled Application Review and Resolution Program, or CARRP, is a covert program that the U.S. government began in 2008. Information about it is still hard to come by, however.
Here are the basics: For national security reasons, the U.S. Department of Homeland Security (DHS), in particular U.S. Citizenship and Immigration Services (USCIS), began giving strict extra scrutiny to immigrants and non-citizens from Arab, Middle Eastern, Muslim, and South Asian communities when they apply for U.S. citizenship, lawful permanent residency (a green card), and asylum.
The typical result of this added scrutiny is that applicants put on the CARRP list face long USCIS delays in the best case, and in the worst, receive a USCIS denial without prior notice, stated reason, or legal authority. In some cases, USCIS will not take any action at all until the FBI tells it what action it would like taken on the application, which can result in indefinite limbo.
The American Civil Liberties Union (ACLU) has been a leading force in attempting to find out more, tracking CARRP's results and bringing legal action in cases where the program has been applied unjustly. (Also see the ACLU report, Muslims Need Not Apply.)
It's not just people who have some sort of black mark on their criminal or immigration record who are entered on the CARRP list. Applicants can be named as national security concerns and put on the U.S.'s "Terrorist Watch List" based on lawful religious activity, country of national origin, a history of travel through areas of "known terrorist activity" (which can be an entire country), and innocuous associations with groups or charities. The ACLU believes that hundreds of thousands of people, including green card holders, are on this list, without even having been advised of this.
For example, if you have given money to a charitable organization that the U.S. government later decides has some association with or provides material support to terrorism, you could be put on the Terrorist Watch List.
Once your immigration case has been flagged for CARRP treatment, USCIS may put your case on hold for 180 days. During that time, either USCIS or the FBI is supposed to conduct an investigation. However, this may drag on indefinitely, and the time period be extended.
You may ultimately be barred from obtaining immigration benefits even if you are otherwise legally entitled to them. What's more, USCIS is reported to routinely come up with excuses or pretexts to deny these cases, such as that the person submitted "false testimony" (even if it's forgetting to report having donated to a particular, innocuous charity many years before).
If you apply for a green card, U.S. citizenship, or some other immigration benefit, you would normally expect to wait a period of months for a decision. Check the USCIS website for the normal processing time. Some delays beyond these times are "normal," as USCIS frequently gets backed up.
If, however, you are from one of the communities listed above, and you find that you have been waiting many weeks more than the normal processing time—or if your interview or similar follow-up is canceled at the last minute without explanation or a postponement—there's a good chance you've been placed on the CARRP list.
Another indicator is if an FBI agent visits you with requests to inform on members of your community.
Because USCIS will not give you any notification of the suspicions about you, and won't offer you any opportunity to counter or respond to them, contacting the ACLU is your best bet if you suspect you may have been placed on the CARRP list. You will likely need the help of an experienced immigration attorney, as well.