Mr. Coello’s problems in the United States most likely began when he became drowsy working as a driver for the ride-hailing service Lyft and pulled over to sleep in a parking lot. A police officer rapped on his window, telling him it was private property and writing him a ticket. He was convicted of misdemeanor trespassing and paid a fine of $100 and $92 in court costs, according to court records in Fairfax, Va.

That conviction brought him to the attention of ICE. “Marco Coello has one misdemeanor criminal conviction and did not depart the country in accordance with his visa,” said Nestor Yglesias, an ICE spokesman, referring to the tourist visa he had arrived on. “As a result, he violated the terms of his nonimmigrant status in the United States.”

Paul Wickham Schmidt, a retired immigration judge who is now an adjunct law professor at Georgetown University, said that ICE agents could legally arrest individuals in asylum proceedings. “Otherwise everyone could absolutely immunize themselves from removal just by filing with the asylum office,” he said.

But arresting Mr. Coello was also indicative of the Trump administration’s new priorities, he said. “As Jeff Sessions keeps pointing out, anyone here illegally shouldn’t feel safe,” Mr. Schmidt said, referring to the attorney general under Mr. Trump.

Mr. Coello was a high school student in El Hatillo in southeastern Caracas when he joined marches and demonstrations across Venezuela on Feb. 12, 2014, to protest Mr. Maduro, a close ally of Hugo Chávez who took office after Mr. Chávez’s death in 2013.

The protests that day turned ugly, with violence between government forces and civilian protesters, who in some cases threw Molotov cocktails. Mr. Coello, who said he was not involved in the disturbance, was struck on the leg by a tear-gas canister and fell to the ground. Security personnel in plainclothes began to beat him and took him into custody.