Federal authorities have arrested a 23-year-old Mexican immigrant who was brought to the United States illegally as a child and who might be the first participant in an Obama-era program for such immigrants to be detained since President Trump took office, reported the Reuters news agency.

In a tweet on Tuesday evening, the National Immigration Law Center called the news “unacceptable and horrifying.”

The immigrant, Daniel Ramirez Medina, has a 3-year-old child and no criminal record. He was detained last week in Washington State at the home of his father, whom U.S. Immigration and Customs Enforcement officers had come to arrest, although it’s not clear why.

Citing a court filing in the case, Reuters reported that Mr. Ramirez had been allowed to live and work in the United States under the Obama administration’s Deferred Action for Childhood Arrivals policy, or DACA, which temporarily put off deportation proceedings against participants in the program. DACA participants, often called “Dreamers,” now number some 750,000 people, many of them college students.

Because President Trump won election in part on the basis of his strong stand against undocumented immigrants, many DACA participants have feared that they would eventually end up the targets of a government crackdown. Mr. Trump’s executive order last month blocking visitors from seven majority-Muslim countries and all refugees only stoked those fears. The order is currently on hold while it faces several lawsuits.

Mr. Ramirez’s lawyers this week challenged his arrest in a petition filed in federal court, saying that the DACA program protected him. One of the lawyers said, “We are hoping this detention was a mistake.”

Late Tuesday a judge at the U.S. District Court in Seattle ordered the federal government to respond to Mr. Ramirez’s petition, The Seattle Times reported. The judge, James P. Donohue, specifically asked the government to explain why Mr. Ramirez was being detained “given that he has been granted deferred action under the Deferred Action for Childhood Arrivals program.” Judge Donohue also asked whether the government planned to deport Mr. Ramirez. A hearing is scheduled for Friday.

Immigration and Customs Enforcement officials declined to comment about the case to Reuters, and the Justice Department is still studying the case, a spokeswoman said.