Carlos Holguín heals through music. 

"For me it's a catharsis. It's a therapy," the 66-year-old said.

As the general counsel at the Center for Human Rights and Constitutional Law, Holguín has to routinely tour detention and shelter facilities where migrant children are housed.

"Visiting these facilities, it takes a day or two to recover. It's not easy to see some of these things but you know, there is no option. One has to look at it and see what we can do to improve things," Holguín said.

He has been trying to improve conditions for migrant children since 1984 when he took on the case of a 15-year-old girl from El Salvador named Jenny Lisette Flores, who immigration authorities had detained.

Holguín and his colleagues at the Center for Human Rights and Constitutional Law alleged the government was indefinitely jailing migrant minors until their parents showed up to claim them.

"If their parents were undocumented it essentially meant that their parents were surrendering for deportation. That was the main thrust of the initial legal complaint that we filed, that it was unfair and unconstitutional for the government to hold children and detain children as bait for the capture of their parents," Holguín said.

Then there was the issue of the children's conditions: kept in dilapidated hotels known for prostitution and drugs with no recreation, visitation or education. According to the lawsuit, kids were forced to share rooms with unrelated adults with little regard for their safety.

The case made it to the Supreme Court. It concluded with the Flores Settlement in 1997, in which the government agreed to three things: to release children to parents or appropriate adults "without unnecessary delay," to place kids in the "least restrictive" setting and to implement standards for their care.

"There was nothing before that that would help these children and regularize their treatment," Holguín said.

Now, Holguín regularly visits emergency intake shelters for migrant kids, like the one at the Pomona Fairplex.

"We are here to interview children to monitor compliance with the Flores Settlement," Holguín said as he walked into the facility.

The Fairplex is one of the dozens of facilities across the country housing hundreds of migrant children after this year's surge in unaccompanied minors. The shelters, including a now-closed one in Long Beach, are different from what Holguín originally witnessed.  

Now, most of them are clean, kids are kept in wide spaces, not cells or small rooms, and children are provided with books, toys and recreation.

However, not all facilities are living up to those standards, and there have been reports of COVID-19 outbreaks and sexual abuse at some shelters, so Holguín is not letting his guard down.

"The question is, are the children being moved out of the facility as quickly as possible and while they remain in the facility are the conditions safe and sanitary?" he said.

Holguín said as long as there are things to fix and people to fight for, he'll keep pushing off retirement.

"I was raised with the idea that one has to try to make the world, at least if not a little better, a little less worse than it would have been but for one's passing."