The family of six say they were stopped at the Canadian border on their way back home to Minnesota. They handed over their U.S. passports and the children’s birth certificates to a Border Patrol officer and waited in the car. Moments later, they say, three border officials emerged from their office, guns drawn and pointed at the family. The children started screaming.

Thus begins Abdisalam Wilwal and Sagal Abdigani’s account of their nearly 11-hour detention at the hands of Department of Homeland Security officials, according a lawsuit filed Thursday on their behalf by the American Civil Liberties Union (ACLU) and a private law firm, Robins Kaplan.

The lawsuit contends the U.S. government violated the constitutional rights of Wilwal, Abdigani and their four children by allegedly subjecting them to unreasonable search and seizure, and violating their right to due process when the family, all of whom are U.S. citizens, tried to reenter the United States on March 30, 2015.

The family’s ordeal, their lawyers claim, stem from Wilwal’s inclusion on the United States’s sprawling terrorist watch list. The case underscores long-running questions about the functionality and due process surrounding the database, said Hugh Handeyside, a staff attorney on the ACLU’s National Security Project. The ACLU says the government placed Wilwal on the watch list without his knowledge and with no known justification.

“The [Customs and Border Protection] CBP officers treated the family this way not because they had probable cause to believe anyone in the family had committed a crime, but because Abdisalam Wilwal’s name appeared on the government’s terrorism-related watch list,” the lawsuit reads.

The FBI, which maintains the watch list known formally as the Terrorist Screening Database (TSDB), said it does not publicly confirm or deny whether a person is on the list, because it “would significantly impair the government’s ability to investigate and counteract terrorism, and protect transportation security,” said Matthew Bertron, an FBI spokesman.

Officers with U.S. Customs and Border Protection (CBP), who were later joined by officers from Homeland Security Investigations (HSI), kept Wilwal handcuffed and secluded for more than 10 hours, even after he fainted and required medical attention, the family says. The officials accused Wilwal of being a terrorist, asked him whether he was Muslim, and denied him access to food. They also denied the family access to a phone and a lawyer, told the couple’s 14-year-old son to undress for a strip search and searched the contents of his phone.

“As a matter of policy, CBP does not comment on pending litigation,” said Jennifer Gabris, CBP a spokeswoman. Officials from Immigration and Customs Enforcement (ICE), the agency that the family’s lawyers say also participated in the detention, did not respond to a request for comment.

As of June 2016, there were approximately 1 million records in the Terrorist Screening Database, according to the FBI. Of those, only 0.5 percent are U.S. citizens, Bertron said.

The lawsuit’s key arguments are these: first, that whatever discretion U.S. border authorities have to detain, search and interrogate people at points of entry — and they have a lot — they are still prohibited from violating a person’s constitutional rights. Border authorities did so by subjecting Wilwal to excessive force and the entire family to unconstitutional seizure, the lawyers say. Second, the lawsuit raises an older issue: while it might remain entirely unclear how a person ended up on the FBI’s watch list, there is no “fair and meaningful” process to seek removal — a fact that civil rights lawyers have long contended stands in violation of citizens’ Fifth Amendment due process rights. (The ACLU has been involved in similar litigation since 2010 regarding the much narrower no-fly list, which also includes U.S. citizens.)

Abdigani and Wilwal, both refugees of Somalia’s civil war in the 1990s, have resided in the United States for 17 years.

The most decisive indication of Wilwal’s watch list inclusion came a few weeks after the family had returned home to Eagan, Minnesota and after the family had launched a complaint at a local DHS office, and repeatedly called the office for follow-up. At that point, Wilwal received a voice mail from a DHS staff member, the lawsuit says. “The staff member stated that the incident at the Portal border station likely occurred because Mr. Wilwal’s name appeared on a terrorist watch list,” it says.

The family, who had traveled to Canada for a few days to visit Wilwal’s sister, also received a vague warning from Canadian border officials when they entered Canada. Wilwal might receive more questioning than usual when he returned, they said according to the lawsuit, because of a notation on his name in their records.

A border security document, recording the family’s arrival and submitted by their lawyers as case evidence, describes “a confirmed subject record hit.”

Because it’s unclear who is on the watch list, it is unknown how many of its members are Muslim, like the Wilwal and Abdigani family.

The Council on American-Islamic Relations (CAIR), a Muslim advocacy group, has alleged that Customs and Border Protection officers discriminate disproportionately against Muslims at airports and border crossings and at a more frequent rate since Trump sought to ban the citizens of seven majority-Muslim countries. While the Wilwal and Abdigani family was detained during the Obama administration, CAIR said earlier this year that it had documented a significant increase in complaints of harassment involving U.S. border authorities’ treatment of Muslims during Trump’s first 100 days in office, rising from 17 during the same period last year to 193 this year.

CBP did not respond to a request for comment on those numbers.

Handeyside said reports received by the ACLU also “suggest that people from Arab, Muslim and South Asian communities have born the brunt — as has long been the case — of these abuses, and have been especially targeted for conduct like this.”

A border official’s summary of the encounter on a document submitted by the family’s lawyers as evidence includes notes about the family’s religion. “It should be noted that WILWAL stated that he and his family do not associate themselves with any type of religion. It should also be noted that during a border search of a cellular telephone belonging to WILWAL’s step son . . . and app called ‘Muslim Pro’ was discovered,” the document reads.

Wilwal and Abdigani declined, through their lawyers, to comment.