Attorneys and activists worry the federal government may be discriminating against people with Muslim-sounding names by revoking their membership in a program that makes it faster to get through airport security.

Greg Siskind, an immigration attorney based in Memphis, Tennessee, told The Daily Beast that in the aftermath of Trump’s first travel ban, he started hearing from people who received vague letters from the Department of Homeland Security informing them that their Global Entry status was being revoked.

Global Entry is part of the DHS’s Trusted Traveler program, which lets travelers get pre-screened so they can have much shorter wait times at airports when returning to the U.S. from other countries. USA Today called it “a great value for any adult who travels domestically and abroad.” To get it, enrollees must go through an extensive background check and an in-person interview.

And for many travelers with Muslim or Arab names—including U.S. citizens—that “great value” has been revoked. So Siskind and another immigration attorney, Andrew Free, have teamed up with the Arab-American Anti-Defamation Committee to seek more information from the Department of Homeland Security—and even take the agency to court, if necessary. They filed a Freedom of Information Act request with the agency on Wednesday, and Free said they are prepared to sue if the department doesn’t provide more information about any changes.

“We’ve got a bunch of people who are telling us that they’ve been revoked, and they all have something in common—and it’s not that they have a different security profile,” said Free. “It’s that they have Muslim-sounding names or are Muslim.”

A Customs and Border Protection spokesperson strongly disputed these allegations.

“The claim you report is completely false,” the spokesperson said. “I can tell you that having a Muslim or Arab sounding name is not a criteria for Trusted Traveler revocation.”

Free added that he and Siskind hadn’t heard of any examples of apparently discriminatory revocations before Trump was inaugurated. But since he came into office, they said they have heard from more than two dozen people who lost their Global Entry for reasons they believe are discriminatory.

“That’s enough to show that there’s something systemic going on,” said Abed Ayoub, the legal director for the American-Arab Anti-Discrimination Committee. “It indicates that this administration has put policies in place to target Arab and Muslim nationals, including Arab and Muslim U.S. citizens.”

“Given the current climate and the president’s promises on the campaign trail, it seems to me that there are serious questions as to whether they’ve effectuated unofficial policies of interfering with the travel of U.S. citizens and others who just happen to be Muslim,” Free said.

The FOIA request, which The Daily Beast reviewed, says that these incidents seem to be part of a pattern.

“ADC has received reports that immediately following the presidential election in November, persons who were granted access to the GES had the privilege revoked by CBP,” it reads. “These are not isolated incidents, it appears, but rather, part of a larger pattern in which GES participants with Arab or Muslim names or ancestry have been singled out for revocation in the absence of any material change in their risk profile. Physicians, bankers, students, and businesspeople—all long-time holders of GES status—have suddenly and inexplicably faced new scrutiny. The vast majority of those reporting revocation are U.S. citizens.”

Mic and Skift reported on the Global Entry revocations in the immediate aftermath of Trump’s first travel ban. Siskind says that in the weeks since then, he and Free have gathered more and more examples of people who have lost their Global Entry status—enough that they are pushing the DHS to turn over more data on the program.

In the meantime, those who lost their Global Entry tell The Daily Beast that they’re confused and concerned. Farhad Hasan, an Iraqi Kurd and a doctor who came to the U.S. to practice medicine, said he lost his Global Entry and that he believes his nationality was the reason.

“It’s inconvenient,” said Hasan, who has a green card and is going through the naturalization process. “It’s like getting discriminated against just based on nationality.”

“I’m a Kurd,” he added. “We were persecuted inside Iraq, and now it’s like we are persecuted even in the U.S.”

And Saeed Mohamed, an American citizen and a Muslim who had his Global Entry revoked in late January, told The Daily Beast that the change perplexed him.

“The government is not so efficient that they can figure everything out,” he said. “They can be very heavy-handed, and I do believe my name is common enough that it could have tripped something. But that should have been a problem the first time I applied, not for them to just out of the blue to revoke everything, especially coming 10 days after the inauguration.”

And Nojan Emad, an Iranian-born citizen of Canada who moved to the U.S. about five years ago, said his Global Entry was revoked shortly after DHS confirmed that he had gotten it. He said his family fled Iran when he was 7 because of the Islamic Revolution, and that he hasn’t been back since.

“I’m positive that this is definitely because of where I was born and because of the Muslim ban, or whatever it’s called—the travel ban this president has put through,” he said. “I’m just appalled. I’m appalled.

“We truly fear what’s happening,” he added. “It’s causing a lot of anxiety.”

And it’s not just people born in Iran and Iraq who have lost their status. Mona Jundy, an immigration attorney based in Flint, Michigan, told The Daily Beast that in the last several weeks, she has heard from several Syrian nationals who lost their Global Entry status and were hoping to get it reinstated. She added that it was the first time she heard any queries about the program. And there is speculation that Khizr Khan—who famously criticized then-candidate Donald Trump at the Democratic National Convention—had his Global Entry status revoked as well.

In the meantime, lawyers are hoping some of the people who lost their Global Entry status will be able to get it reinstated.

“I can assure you the U.S. citizen doctors were not doing sleeper cell work between surgeries,” said Siskind.