The border agent, identified in the lawsuit as Paul O’Neal, stopped the women, Ana Suda and Martha Hernandez, inside a convenience store in Havre, Montana, late on May 16.

The lawsuit alleges that he commented on Hernandez’s accent, calling it “very strong,” and then asked where they were born. Hernandez was born in California and Suda in Texas, the ACLU said.

When the women expressed shock at the agent’s question, he told them he was “dead serious” and asked to see their identification, the lawsuit alleges.

After they showed the agent their valid Montana driver’s licenses, he briefly detained them in the store’s parking lot, the lawsuit contends. The women then began to shoot video of the encounter on their phones and asked the agent on video why they were being stopped.

“Ma’am the reason I asked you for your ID is I came in here and I saw you guys are speaking Spanish, which is very unheard of up here,” the agent said, looking into the camera.

One of the women then asked if they had been stopped because of their “racial profiles.”

“No, it has nothing to do with that,” he replied, according to the video. “It’s the fact that it has to do with you guys speaking Spanish in the store in a state where it is predominantly English-speaking, OK?”

The ACLU says that is not OK. In the lawsuit, filed in U.S. District Court for the District of Montana, it alleges that Customs and Border Protection violated the Fourth Amendment to the Constitution because the agency did not have probable cause to detain the women.

It also argues that the agency violated the women’s constitutional right to equal protection because the agent said he was questioning them because he heard them speak Spanish, which the ACLU argues was used as a proxy for their race.

A spokesman for Customs and Border Protection declined to provide information about the encounter or to comment on the lawsuit, which also names O’Neal, acting Customs and Border Protection Commissioner Kevin McAleenan and 25 unnamed “John Doe” defendants the ACLU said were involved in the episode.

“As a matter of policy, U.S. Customs and Border Protection does not comment on pending litigation,” Jason Givens, an agency spokesman, said in an email. “However, lack of comment should not be construed as agreement or stipulation with any of the allegations.”

Efforts to locate O’Neal on Thursday evening were not immediately successful.

In a statement, the ACLU said that it was unconstitutional for law enforcement or immigration agents to detain people because of their language, accent or race. Cody Wofsy, a lawyer with the organization’s Immigrants’ Rights Project, said he saw the case “as a part of a broader pattern of abusive conduct by an out-of-control agency.”

“This is an opportunity for the courts to step in and say there are constitutional limits on what CBP can do,” he said. “This is certainly nothing new based on what we have seen over the last couple of years of the Trump administration. The agency has been emboldened to act on some of its worst impulses.”

The case highlights concern over the far-reaching power of Customs and Border Protection, whose agents have the authority to detain and question people up to 100 miles from an international border, a vast area that is home to almost two-thirds of the U.S. population.

Havre, a remote farm city of about 9,000 people, is home to a Customs and Border Protection field office with 183 agents who have jurisdiction over more than 450 miles of the Canadian border. The city is about 35 miles from the border.

In 2006, the 9th U.S. Circuit Court of Appeals ruled that border agents illegally detained five Latino men in Havre in 2004 and said that “apparent Hispanic ethnicity, although a relevant factor in the reasonable suspicion inquiry, cannot by itself justify an investigatory stop in a border area.”

The episode on May 16 was not Suda’s and Hernandez’s first experience with border agents.

According to the lawsuit, the women were dancing at a bar last February when a plainclothes border patrol agent took a picture of them on his phone and sent it to other agents with the comment, “There are two Mexicans at the bar.”

One of the agents receiving the text responded that the women were friends of his wife, the ACLU said.

Hernandez and Suda were detained in the parking lot for about 40 minutes last May, the ACLU said. During their detention, several more agents, including O’Neal’s supervisor, arrived on the scene, according to the lawsuit.

Suda asked the supervisor, who was not identified by name in the lawsuit, if they would have been detained if they had been speaking French.

“No,” he replied, according to the lawsuit. “We don’t do that.”

In a statement, Suda said the experience had been humiliating and had led other Havre residents to shun them. Suda said her daughter was afraid to speak Spanish and now responds in English when her mother speaks to her in Spanish “because she is scared.”

“This changed our lives, I believe, forever,” Suda said in the statement.

This article originally appeared in The New York Times.