The Terrorist Screening Database, a federal list of terror suspects, is a secret list compiled by the FBI, and it’s impossible for people to verify whether or not they have been included on it.

But lawyers from designated terrorist group CAIR (Council on American-Islamic Relations), who filed the lawsuit on behalf of the plaintiffs, say people who are on the list know they were included because they are frequently harassed by law enforcement officials and consistently have their rights violated. Often they are singled out at airports by having the letters SSSS stamped on their boarding passes.

“There is no confirmation, but it’s something that we gather from these individuals’ experiences,” Nikiya Natale, a legal director for CAIR in Texas, told Newsweek. “At CAIR we encourage people to report anti-Muslim bias and any sort of hate or bias they experience, and we respond to cases of discrimination or harassment.”

Abraham Sbyti, a 45-year-old based in Texas, told Newsweek he has been stopped and questioned by law enforcement officials in airports 24 times since 2014. Sbyti, who is employed as an air-conditioning technician, is originally from Iraq and was re-settled in the U.S. as a refugee in 2000. He obtained citizenship in 2005 and lives with his wife in Texas, but he visits his mother in Lebanon a few times a year.

“All of a sudden, after November 2014, I found myself getting randomly searched at the airport. In 2014 they started searching me; I went through the search. They said it was a random check. They started asking me if I go to the mosque, and I answered all of their questions,” Sbyti explained to Newsweek.

“This has happened 24 times—every time I leave the country. They are so nice in America, honestly, they are nice. But my wife and I have to wait hours while they ask questions.”