LOS ANGELES — Some immigrant youth looking to start over in the United States after fleeing abusive homes are seeing their applications for green cards rejected because the Trump administration says they’re too old.

A U.S. government program in place since 1990 has let young immigrants subject to abuse, abandonment or neglect by a parent seek a court-appointed guardian and a green card to stay in the country.

While applicants must file paperwork before age 21, the Trump administration has said some are too old to qualify once they turn 18, prompting a flurry of denial notices over the past year in New York, Texas and California and additional questions of applicants in New Jersey.

Immigrant advocates have filed lawsuits in New York and California and said hundreds of young people could be affected by the change.

“This administration is literally going after some of the most vulnerable people trying to seek relief,” said Mary Tanagho Ross, an appellate staff attorney at Los Angeles-based Public Counsel’s immigrant rights project.

The Trump administration has been pushing to harden the U.S. border and slash immigration with a series of steps targeting Central American children who arrive on the border alone or with relatives. Former Attorney General Jeff Sessions sought to make it tougher for young immigrants fleeing gangs or domestic violence to win asylum — though some guidance he issued on such cases was recently blocked by a federal judge. And the U.S. government has been slower to release immigrant children caught on the border to family in the country.

The program is the best chance for many of the thousands of young immigrants arriving on the border to be allowed to stay in the U.S. Under U.S. law, they can apply for green cards once a designated court in the U.S. state where they live assigns them a guardian and declares they are eligible to apply.

A now-22-year-old woman in Northern California, who requested anonymity out of fear the U.S. government will retaliate against her for speaking out, fled her Mexican immigrant parents’ home in high school after her father repeatedly beat her.

She was taken in by a teacher, who helped her get started in college and took care of her when she was diagnosed with cancer. When a judge formally named the teacher her legal guardian it was a huge relief, she said. But she later learned the U.S. government wouldn’t accept the court’s order for her green card application. She dropped to the floor and sobbed, she said.

“I just couldn’t believe I was going to have to try to defend myself again,” she said. “I don’t refer to her by her name or that she’s my guardian — I just call her mom.”

More than 50,000 young immigrants have obtained green cards by qualifying for special immigrant juvenile status since 2010. The overwhelming majority of applications have been approved by U.S. Citizenship and Immigration Services, making the program a safer bet for many immigrant children seeking refuge in the United States than pleading a case before an immigration officer or judge for asylum.