“People say they are scared, but we don’t have to be invisible anymore,” Ms. Mateo told hundreds of students when she was honored by a Northridge student group this spring. “You’re safer when you are out, when you are connected to people who will know if ICE comes for you in the middle of the night.”

Those who advocate for a stricter crackdown on illegal immigration strongly disagree.

“To say ‘I am here illegally and I don’t care about what the law says and I am just going to be here and I demand to be rewarded for it,’ that tends not to play well,” said Ira Mehlman, a spokesman for the Federation for American Immigration Reform, which advocates more immigration restrictions. “If you are in the country illegally, there is no reason you should be able to practice law.”

Mr. Reyes Savalza, 29, who was also born in Mexico, knew about Ms. Mateo long before he met her. He had seen her speak at rallies and read about her protests for years. Her brand of activism inspired him while he was studying at New York University School of Law. When he was offered to take on her case, he did not hesitate.

As a child, Mr. Reyes Savalza’s mother taught him to tell anyone who asked that he was born at O’Connor Hospital in San Jose, Calif. When he began working as a teenager he used a fake Social Security number to get a job, as a vast majority of undocumented immigrants do. That is now considered grounds for deportation.

For the past two years, Mr. Reyes Savalza has worked at Pangea Legal Services, a nonprofit in San Francisco that helps defend immigrants from deportations. These days, as Mr. Trump moves forward with his vows to increase deportations throughout the country, Mr. Reyes Savalza, who has legal status through DACA, sees his job as more difficult.

He worries about his parents, anxious that any phone call could be the one to inform him that they were picked up by immigration officers. Like his clients, they want answers he does not have.

“They want me to tell them everything will be O.K., but I can’t,” he said.

Between the two of them, Ms. Mateo and Mr. Reyes Savalza are working to help more than a dozen undocumented immigrants remain in the country. As her lawyer, Mr. Reyes Savalza plans to resubmit Ms. Mateo’s application for DACA in the coming weeks. Ms. Mateo will soon begin working on her two younger brothers’ applications for renewal.