Increasing border detentions and a ballooning American watchlisting system are two major drivers of government abuse. A lawsuit the ACLU filed last week challenges both.

We represent Abdisalam Wilwal, Sagal Abdigani, and their four young children — all U.S. citizens whose experience at the border represents much of what’s wrong with the government’s approach to border security.

The family lives in the Minneapolis area and was returning from a trip to visit relatives in Saskatchewan, Canada, on March 30, 2015. After they pulled their minivan up to the border checkpoint at Portal, North Dakota, U.S. Customs and Border Protection officers appeared with their guns drawn and pointed at the van, yelling at Abdisalam to come out with his hands in the air. They handcuffed him in front of his family as his children screamed and cried from fear.

The officers held Abdisalam for almost 11 hours, which he spent handcuffed alone in a room in the border station. At one point during the detention, having been denied food or water for hours, he passed out and required medical attention.

The officers detained Sagal and the four children elsewhere in the border station. They denied her requests to use the phone or have someone pick up the children, saying, “You’re all the same. You’re all detainees, including the children.” At one point hours into the detention, Sagal — extremely anxious about her family’s safety — used her son’s phone to call 911 and report what was happening. A CBP officer grabbed the phone and spoke to the dispatcher. Help never arrived.

Two officers then took Sagal’s son, who was 14 years old at the time, into a separate room and patted him down. They told him to remove his clothes for a strip search, which he refused to do.

About nine hours into the detention, two Homeland Security Investigations agents arrived at the border station. They questioned Abdisalam for about 45 minutes about his religious practices, travel, family, and job. They then told him he was free to go. The whole family left immediately.

Read more about the family’s harrowing experience

Abdisalam later learned that he and his family were detained because he is on the government’s terrorism watchlist. He doesn’t know why he’s been watchlisted, and the government won’t tell him.

This much is clear, though: The officers’ treatment of the family violated the Constitution. The Fourth Amendment protects against unreasonable searches and seizures, and what happened to this family was anything but reasonable.

The fact that it happened at the border doesn’t matter. We frequently hear that CBP officers tell travelers, including U.S. citizens, that they don’t have rights at the border. That’s flat wrong. CBP officers do have the authority to conduct what are called “routine searches” — they can stop people at border crossings and search their belongings without a warrant or suspicion that they’re engaged in wrongdoing. But officers can’t use unreasonable force, and a lawful border stop can become an unlawful seizure or arrest if the officers have no valid reason to prolong the stop.

The CBP officers who detained Sagal and the kids had no basis to believe that they were either inadmissible to the United States or carrying contraband, but the officers nonetheless held them captive for nearly 11 hours. That’s an unlawful seizure. And what the officers did to Abdisalam amounted to an arrest without a warrant or probable cause: They displayed and used force to handcuff him, hold him alone and against his will, and interrogate him without advising him of his right to remain silent or contact an attorney.

The fact that Abdisalam was on a government watchlist doesn’t provide cause for the officers’ treatment of him or his family. Leaked documents show that the government uses vague criteria and a very low threshold to place people on the terrorism watchlist, which has ballooned to approximately 1 million people. According to the government’s own watchlisting rules, “concrete facts are not necessary” to meet the standard for placement on the watchlist, and uncorroborated information of questionable or even doubtful reliability can suffice. Such lax criteria open the door to relying on rumor, innuendo, or false statements to place people on the watchlist.

That leads to the second major constitutional issue that this border detention raises: violation of the Fifth Amendment’s due process guarantee. The government denies people due process when it places them on a secret blacklist and then harasses, abuses, or detains them on that basis, without giving them notice of the reasons why and a meaningful opportunity to contest those reasons. Abdisalam learned he’s on the watchlist from a government document that the ACLU obtained through the Privacy Act, but the government has refused to tell him why he’s been watchlisted or give him a chance to clear his name and get off the list.

Returning to America from abroad should not mean forfeiting our constitutional rights. The government must adopt policies to ensure that what happened to Abdisalam, Sagal, and their children doesn’t happen again.