A 23-year-old Mexican man who was brought to the US illegally at the age of seven has been arrested and detained, despite having a valid work permit.
Daniel Ramirez Medina was protected from deportation under one of President Barack Obama’s policies.
He has a job, a young son and no criminal record.
Mr Ramirez was taken into custody on Friday and is being held in Tacoma, Washington.
US Immigration and Customs Enforcement (ICE) agents had intended to arrest his father at home in Seattle, but also detained Mr Ramirez.
In a statement, an ICE spokeswoman said the 23-year-old had told agents he was a gang member, and was taken into custody for being a “risk to public safety”.
Mark Rosenbaum, one of Mr Ramirez’s lawyers, said he “unequivocally denies being in a gang”.
He said Mr Ramirez had been “repeatedly pressured” by customs agents to falsely admit to gang links while in custody.
Mr Ramirez’s legal team say this could be the first time under the Trump administration that a person covered by the Deferred Action for Childhood Arrivals, or DACA, has been taken into immigration custody.
DACA was established in 2012 by President Obama to allow those brought to America while young to attend school and work without fear of deportation.
There are more than 740,000 people in the programme.
They are often known as “dreamers” – a name taken from the failed 2010 DREAM Act (Development, Relief and Education for Alien Minors) – a bill which aimed to help young illegal immigrants become US citizens.
The arrest is being seen as significant given Mr Trump’s long-standing promise of an immigration clampdown.
In January, he issued an executive order expanding the remit of Homeland Security officials so they can target not only immigrants with serious criminal records, but also those with minor offences or no convictions to their names.
Hundreds of undocumented migrants have been arrested in recent days, in at least 11 states.
‘Keeping my campaign promise’
“The crackdown on illegal criminals is merely the keeping of my campaign promise,” the president wrote on Twitter. “Gang members, drug dealers & others are being removed!”
Mr Trump said he would scrap DACA during his election campaign, but his policy on those it already covers is not yet clear.
In an interview with ABC News last month, President Trump said they “are here illegally” but “shouldn’t be very worried”.
“I do have a big heart,” he said. “We’re going to take care of everybody.”
Mr Ramirez has filed a lawsuit challenging his detention, which states: “The agents who arrested and questioned Mr Ramirez were aware that he was a DACA recipient, yet they informed him that he would be arrested, detained and deported anyway, because he was not ‘born in this country,'”.
A hearing in the case is due on 17 February.
Democrats have raised concerns over Mr Ramirez’s situation, and called for his release.
New York Senator Chuck Schumer tweeted: “DACA recipients should not be an ICE priority. They are young people working & contributing to this great country.”
“ICE must provide answers & release Daniel immediately. This action does nothing to make our country safe.”